This was CNBC's live blog tracking developments on the war in Ukraine for May 15, 2023. See here for the latest updates. 

China's attempts to broker a peace deal between Ukraine and Russia step up a gear this week, with Beijing's special envoy set to visit both countries on a peace mission.

Beijing's special representative on Eurasian affairs, Li Hui, is visiting Europe for talks "on a political settlement of the Ukraine crisis," China's Foreign Ministry said Friday, with the envoy set to visit Ukraine and Russia as well as Poland, France and Germany for talks "on a political settlement of the Ukraine crisis."

There is skepticism over Beijing's ability to manage and resolve a conflict as complex, bitter and deeply entrenched as the one between Ukraine and Russia. Its neutrality has also been questioned because of its closeness to Moscow.

Meanwhile, Ukraine President Volodymyr Zelenskyy is visiting the U.K. on Monday as Kyiv tries to drum up more military support ahead of a highly anticipated counteroffensive.

Ukraine claimed more gains in the besieged and largely ruined town of Bakhmut in Donetsk, eastern Ukraine, this weekend. Fighting has been raging there for months between Ukrainian forces and mainly mercenary fighters belonging to the Wagner Group.

The town holds little strategic value to either side, but after nine months of intense combat there, winning back the town has a deep symbolic importance for Ukraine.

The Wagner Group's leader has complained of a lack of ammunition supplies for his troops in Bakhmut amid a very public dispute with the Russian Defense Ministry.

U.S. joins international coalition to document damage to Ukrainian infrastructure

The Biden administration will join an international coalition responsible for documenting claims of damage to Ukraine's infrastructure as a result of Russia's invasion.

In November, the United Nations General Assembly passed a resolution recommending the creation of an international register of damage caused by Russia's "internationally wrongful acts" in Ukraine.

"In establishing such a register, the Council of Europe is taking an important step to hold Russia to account for its war of aggression. The United States plans to provide funding, working with Congress, to support the Register," U.S. Ambassador to the United Nations Linda Thomas-Greenfield wrote in a statement.

 "Together with the Council of Europe, we stand with Ukraine," she added.

— Amanda Macias

White House set to announce additional sanctions for Iran's military support to Russia

The White House said it will impose additional sanctions targeting Iran as Washington ups the ante in its campaign against Tehran for supplying Moscow with weapons for its war on Ukraine. 

"In the coming days we will be announcing additional designations against those involved in the increased military trade between Russia and Iran," national security council spokesman John Kirby said on a call with reporters.

Kirby added that since August, Iran has provided Russia with more than 400 one-way attack unmanned aerial vehicles, or UAVs.

"By providing Russia with these UAVs, Iran has been directly enabling Russia's war of aggression in Ukraine," he added.

— Amanda Macias

Banksy artwork removed from damaged residential building

Workers moved to preserve part of a wall with the work of world-renowned graffiti artist Banksy in the town of Irpin, located outside Kyiv.

The artwork was from a residential building that was heavily damaged during Russia's attack on the town.

-Reuters

One ship leaves Ukraine's port of Odesa as expiration of Black Sea Grain Initiative looms

One ship carrying 19,800 metric tons of sunflower meal left Ukraine's ports of Odesa under the Black Sea Grain Initiative. The ship is destined for Morocco.

The Black Sea Grain Initiative, which established a humanitarian sea corridor, more than 900 ships carrying 30 million metric tons of agricultural products have departed from Ukraine's war-weary ports. Russia has previously said that it would not recognize an extension of the deal, which could expire in mid-May.

— Amanda Macias

Poland gets 1st U.S.-made HIMARS rocket launchers

Poland has received its first shipment of HIMARS rocket launchers to strengthen its artillery amid security concerns due to the war in neighboring Ukraine, the Associated Press reported.

The High Mobility Artillery Rocket System — produced by American aerospace company Lockheed Martin — is a multiple rocket launcher with a range of up to 300 kilometers (190 miles). Poland is spending about $414 million (380 million euros) to buy 18 advanced combat HIMARS launchers and two HIMARS training launchers, with ammunition and related equipment, according to the AP report.

Defense Minister Mariusz Blaszczak said that combat in Ukraine had proven the value of the HIMARS.

"We are watching the developments in Ukraine, and we know that artillery has a key role in the war, in repelling the Russian invasion," Blaszczak said in the AP report.

— Melodie Warner

Zelenskyy holds meetings in Italy, the UK, France and Germany to discuss additional security assistance

Ukrainian President Volodymyr Zelenskyy thanked the leaders of Italy, Germany, France and the United Kingdom for meeting with him to discuss additional security assistance for Ukraine.

Zelenskyy, who traveled to the European capitals, said in a statement following the visits that "important agreements were reached on defense support."

"The position of each of these countries is very important here. And it is important that this position is united," Zelenskyy said, adding that some discussions involved the creation of a coalition of fighter jets for Ukraine.

The Ukrainian leader also said that he was given an update on the upcoming G7 meetings.

— Amanda Macias

UN calls for the safe passage of humanitarian convoys to Ukrainian cities under Russian military control

A United Nations official said that humanitarian teams have not been able to deliver assistance to certain Ukrainian communities since Russia's war in Ukraine began last February.

"Many communities along the north-eastern border with the Russian Federation and near the front line are encircled, cut off from water, food and medical care by heavy ground fighting and blocked roads," Martin Griffiths, under secretary for humanitarian affairs and emergency relief coordinator, said before the U.N. Security Council.

Griffiths said that interagency convoys have not been able to provide humanitarian assistance to Donetsk, Luhansk, Kherson and Zaporizhzhia.

"Under international humanitarian law, all parties must allow and facilitate the rapid and unimpeded passage of humanitarian relief for civilians in need and must ensure that personnel have the freedom of movement required for their work," he added.

— Amanda Macias

At least 8,800 killed in Ukraine since start of war: UN

The United Nations has confirmed 8,836 civilian deaths and 14,985 injuries in Ukraine since Russia invaded its ex-Soviet neighbor in February 2022.

The Office of the U.N. High Commissioner for Human Rights said the death toll in Ukraine is likely higher because the armed conflict can delay fatality reports.

The international organization said most of the civilian casualties recorded were caused by the use of explosive weapons with a wide impact area, including shelling from heavy artillery and multiple launch rocket systems, as well as missiles and airstrikes.

— Amanda Macias

UK has no plans to send fighter jets to Ukraine, PM's spokesman says

Britain has no plans to send fighter jets to Ukraine after the Ukrainian military indicated it would prefer to use F-16 fighter jets, Prime Minister Rishi Sunak's spokesman said on Monday.

Asked if Britain would send fighter jets to Ukraine, the spokesman said: "There are no plans to do that."

"The Ukrainians made the decision to train their pilots on F-16s and you will know the RAF don't use those," he said.

 — Reuters

Kremlin slams new weaponry for Kyiv but says it won't change the course of the war

The Kremlin said Monday that it takes a very dim view of the U.K.'s decision to provide more military hardware to Ukraine but claimed it wouldn't change the course of the war, or "special military operation," as it calls its invasion.

"We feel extremely negative about this," Kremlin press secretary Dmitry Peskov told reporters Monday, in comments translated by NBC News.

"The U.K. claims to be at the forefront among the countries that continue to pump weapons into Ukraine," he added.

The U.K. said last week that it will provide Storm Shadow long-range precision missiles to Ukraine, and on Monday it said it would give Kyiv hundreds of air defense missiles and long-range attack drones with a range of over 200 kilometers, or 124 miles.

The latest announcement came as Ukraine's Zelenskyy visited Britain, one of Kyiv's staunchest supporters.

Peskov downplayed the significance of the latest weaponry that's been announced for Kyiv, saying: "We repeat once again, this cannot have any significant and fundamental impact on the course of the special military operation, but, of course, it leads to further destructions, it leads to further retaliatory actions. That is, it makes this story much more difficult for Ukraine."

— Holly Ellyatt

UK and Ukraine discuss fighter jets, Zelenskyy says decision on the issue could come soon

Ukraine's President Volodymyr Zelenskyy said he and his British counterpart Rishi Sunak discussed the matter of fighter jets for Ukraine as they met in Britain on Monday, hinting that a decision could soon be made on the matter.

Kyiv has repeatedly asked its Western allies for fighter jets, saying they could make a big difference as it tries to reclaim Russian-occupied territory.

"We want to create a fighter jets coalition," Zelenskyy said Monday, following talks with Sunak, Reuters reported.

"I see that in the closest time, you will hear some, I think, very important decisions but we have to work a little bit more on it," he added.

As Zelenskyy's surprise visit to the U.K. was announced Monday morning, Downing Street issued a statement in which it said it would launch a training program for Ukrainian pilots in summer, saying "this will adapt the programme used by U.K. pilots to provide Ukrainians with piloting skills they can apply a different kind of aircraft."

This training, the government added, "goes hand in hand with U.K. efforts to work with other countries on providing F16 jets – Ukraine's fighter jets of choice."

The U.K. has previously ruled out giving Ukraine fighter jets, as has the U.S., but the latest comments signal a change of position could be on the cards.

– Holly Ellyatt

China's envoy will begin Ukraine visit on Tuesday

A top Chinese envoy's visit to Ukraine is due to take place on Tuesday and Wednesday, according to media reports.

Li Hui, China's special representative for Eurasian affairs and former ambassador to Russia, will be visiting Ukraine, Russia and several other European cities in a trip Beijing says is aimed at discussing a "political settlement" to the Ukraine war, which China describes as a "crisis."

Reuters and NBC News both cited an unnamed Ukrainian government official as confirming the visit would begin Tuesday but declined to provide further details.

Ukraine's President Volodymyr Zelenskyy is in the U.K. on Monday to drum up more support for Kyiv ahead of its much-anticipated counteroffensive.

— Holly Ellyatt

UK set to give more aid to Ukraine as Zelenskyy visits Britain

Britain's Prime Minister Rishi Sunak has welcomed his Ukrainian counterpart Volodymyr Zelenskyy to his countryside residence in a surprise visit by the president.

The British government is expected to "confirm the further U.K. provision of hundreds of air defence missiles and further unmanned aerial systems including hundreds of new long-range attack drones with a range of over 200km," or 124 miles.

"These will all be delivered over the coming months as Ukraine prepares to intensify its resistance to the ongoing Russian invasion," Downing Street said in a statement.

During their meeting today at the prime minister's official countryside residence Chequers, Sunak will discuss with Zelenskyy what support Ukraine needs from the international community, both in terms of immediate military equipment and long-term defenses, the government said.

Zelenskyy's trip to today comes after the Ukrainian president's tour of several European capitals in recent days as he tries to win more military support ahead of the country's much-vaunted counteroffensive in Ukraine.

"This is a crucial moment in Ukraine's resistance to a terrible war of aggression they did not choose or provoke," Sunak said in a statement.

"We must not let them down. The frontlines of Putin's war of aggression may be in Ukraine but the fault lines stretch all over the world. It is in all our interest to ensure Ukraine succeeds and Putin's barbarism is not rewarded," he added.

The U.K. is one of Ukraine's largest military supporters, providing masses of military hardware including armored vehicles, tanks and ammunition as well as training to thousands of Ukrainian soldiers. The U.K. said it had provided £2.3 billion ($2.9 billion) worth of military support to Ukraine in 2022 — more than any country other than the U.S.

Last week, the U.K. donated long-range Storm Shadow precision missiles to Ukraine which it said could be "critical in helping the country defend against the relentless bombardment of their critical national infrastructure."

The government also hinted it could be galvanizing support among Ukraine's allies to get fighter jets to Kyiv after repeated requests by Ukraine.

Britain will launch "an elementary flying phase for cohorts of Ukrainian pilots to learn basic training" this summer and said "this will adapt the programme used by U.K. pilots to provide Ukrainians with piloting skills they can apply a different kind of aircraft."

"This training goes hand in hand with U.K. efforts to work with other countries on providing F16 jets – Ukraine's fighter jets of choice," the government said.

— Holly Ellyatt

Ukraine's President Zelenskyy makes surprise visit to the U.K.

Ukraine's President Volodymyr Zelenskyy is set to visit British Prime Minister Rishi Sunak on Monday.

"Today — London. The U.K. is leading the way when it comes to expanding our capabilities on the ground and in the air," Zelenskyy said on Telegram as he announced the surprise visit.

"This cooperation will continue today. I will meet my friend Rishi. We will conduct substantive negotiations face-to-face and in delegations."

Zelenskyy has met with other European leaders in recent days as he tries to drum up more military support for Ukraine as it prepares to launch a counteroffensive. The U.K., one of Ukraine's staunchest supporters, said last week that it would supply Kyiv with long-range missiles.

— Holly Ellyatt

Advance in Bakhmut is first success, Ukraine top commander says

The defense of Bakhmut continues and recent days have shown that Ukraine can move forward and counter the Russian forces there, the commander of Ukrainian ground forces Colonel general Oleksandr Syrskyi said on Monday.

"The advance of our troops along the Bakhmut direction — that is the first successful offensive operation in the city's defence," Syrskyi, was quoted as saying on Ukraine's Media Military Centre Telegram messaging platform.

"The last few days have shown that we can move forward and destroy the enemy even in such extremely difficult conditions ... The operation to defend Bakhmut continues. All necessary decisions for the defence have been made."

— Reuters

Ukraine claims more advances in embattled Bakhmut

Ukraine claimed more gains in the besieged and largely ruined town of Bakhmut in Donetsk, eastern Ukraine.

Ukrainian Deputy Defense Minister Hanna Maliar said on Telegram Sunday that Ukrainian forces "continue to move forward in the Bakhmut sector in the suburbs."

"Today our units captured more than ten enemy positions in the north and south of Bakhmut's outskirts and cleared a large area of forest near Ivanivske. Enemy soldiers from different units were captured," she said in comments translated by NBC, saying the gains had been made "against all odds."

"Anyone who knows the real situation and is there now understands the urgency of the situation. This is when 1 meter is worth 10 kilometers in terms of difficulty of executing tasks," she said, adding that Ukrainian fighters there were "acting on the verge of superhuman capabilities."

Describing the situation in Bakhmut as "very hot," Maliar said Russia had "gathered all its forces there and is trying to advance, destroying everything in its path" and that fierce battles continue.

Fighting has been raging in Bakhmut for months between Ukrainian forces and mainly mercenary fighters belonging to the Wagner Group, descending in recent months into a bloody stalemate.

In recent days, however, Ukraine appears to have redoubled efforts to push Russian forces out of parts of the town they've been occupying.

Russia's Ministry of Defense said Sunday evening that Ukraine's forces had made "made massive attempts to break through the defenses of our troops" to the north and south of Bakhmut while Russian troops continued to try to capture western quarters of the town, which it calls Artemovsk. It claimed its forces had repelled all of Ukraine's attacks.

CNBC was unable to verify the claims by either side.

Bakhmut holds little strategic value to either side but after nine months of intense combat there, winning back the town has symbolic meaning for Ukraine and is important for morale.

The Wagner Group's leader has complained of a lack of ammunition supplies for his troops in Bakhmut amid a very public dispute with the Russian Defense Ministry.

— Holly Ellyatt

China's special envoy heads to Europe in search of peace

China's attempts to broker a peace deal between Ukraine and Russia step up a gear this week, with Beijing's special representative on Eurasian affairs, Li Hui, visiting Europe for talks "on a political settlement of the Ukraine crisis," China's Foreign Ministry said Friday.

Li will visit Ukraine and Russia as well as Poland, France and Germany for talks "on a political settlement of the Ukraine crisis," China's foreign ministry said last Friday.

The ministry noted that "since the beginning of the Ukraine crisis, China has held an objective and just position and actively promoted talks for peace" and said its peace plan "takes into account the legitimate concerns of all parties."

"This upcoming visit by the Chinese representative again reflects China's commitment to promoting peace talks and staying on the side of peace."

The world continued to experience the "spillover effects of the crisis," China said, adding that it aimed to "continue to play a constructive role and build more international consensus on ending hostilities, starting peace talks and preventing escalation of the situation, and help facilitate a political settlement of the Ukraine crisis."

China has tried to position itself as a peace broker since early on in the war, but there is skepticism over Beijing's ability to manage and resolve a conflict as complex, bitter and deeply embedded as the one between Ukraine and Russia.

Read more on the story here: China doesn't really care who wins the war in Ukraine — it just wants to win the peace, analysts say

Read CNBC's previous coverage here:

Russia denies reports of Ukrainian breakthrough in front line