This was CNBC's live blog tracking developments on the war in Ukraine.

U.S. military assistance to Ukraine has "ground to a halt," with Congress yet to authorize the emergency spending requested by President Joe Biden's administration in late October.

In a White House press briefing on Thursday, National Security Council Spokesperson John Kirby said Washington had "issued the last drawdown package that we had funding to support."

"And that's why it's critical that Congress move on that national security supplemental request and we get more funding. The assistance that we provided has now ground to a halt," he said.

Ukrainian President Volodymyr Zelenskyy on Thursday thanked Estonia and Latvia after meeting with leaders of the two Baltic nations to discuss further military aid and Ukraine's path toward EU and NATO membership.

"We must win this battle, not only because the fate of our country and all nations that border Russia is at stake. What is at stake is how global freedom will be treated now and in the future, for our children and grandchildren," Zelenskyy wrote in a post on X.

The Ukrainian leader on Thursday rejected the idea of a cease-fire with Russia, saying it would benefit Moscow, giving it time to replenish its weapons stocks.

Ukraine's armed forces said on Telegram Friday that 64 combat clashes took place the previous day, with Russian forces launching three airstrikes and 16 attacks from rocket salvo systems on Ukrainian positions.

More than 130 settlements in the Chernihiv, Sumy, Kharkiv, Luhansk, Donetsk, Zaporizhzhia, Dnipropetrovsk, Kherson, and Mykolaiv regions came under artillery fire.

"As a result of Russian terrorist attacks, unfortunately, there are dead and wounded among the civilian population," the Armed Forces of Ukraine added, according to a translation.

Ukraine needs more attack aircraft for war effort - ground forces commander

Ukraine's ground forces commander said on Friday that Kyiv needed more military aircraft for its war
effort, such as U.S. A-10 attack jets to support infantry and planes that could fire long-range cruise missiles.

Colonel-General Oleksandr Syrskyi spoke to Reuters in an exclusive interview at an undisclosed location in the northeastern region of Kharkiv that borders western Russia.

"I would talk about A-10s as an option if they'll be given to us ... this is not a new machine, but a reliable one that has proven itself in many wars, and which has a wide array of weapons for destroying land targets to help the infantry," said the 58-year-old, wearing combat fatigues.

The A-10 Thunderbolt is a subsonic attack aircraft produced in the United States that has been in service since the 1970s.

Syrskyi's call for more aircraft comes as a major new U.S. package of military aid for Kyiv has been held up by infighting among lawmakers.

Syrskyi said the A-10 would provide crucial support for ground forces as they attempt to seize the initiative against a well-resourced enemy.

"It is for destroying land-based targets: tanks, artillery ... everything that counters the infantry," he said.

Sirskyi added that attack helicopters such as the AH-64 Apache and AH-1 Super Cobra, as well as the UH-60 Black Hawk, could also play an important role.

— Reuters

UK PM Sunak signs security agreement with Ukraine, announces further defense support

Ukrainian President Volodymyr Zelenskyy and U.K. Prime Minister Rishi Sunak on Friday signed an agreement enhancing the countries' security co-operation.

Zelenskyy described the agreement as "unprecedented" and a "basis for working with other partners" during Sunak's trip to the Ukrainian capital Kyiv.

It commits the U.K. to providing "comprehensive assistance to Ukraine for the protection and the restoration of its territorial integrity within its internationally recognised borders."

The U.K. also pledged to support Ukraine's efforts to join the NATO security alliance and support prevention and counter-measures against any military escalation or acts of aggression by Russia.

It comes after the U.K. announced a package of Ukraine defense support worth £2.5 billion ($3.19 billion), including production of thousands of military drones, and £18 million in humanitarian aid.

— Jenni Reid

Russia's Medvedev says UK troop deployment in Ukraine would be 'declaration of war'

Former Russian Prime Minister Dmitry Medvedev said on Friday that any deployment of British troops to Ukraine would be a declaration of war, as U.K. Prime Minister Rishi Sunak visited Kyiv to announce an increase in military funding to finance a new range of drones.

"What would Western public say, if the British representatives happened to be bombarded with cluster ammunition in the centre of Kiev, just as was the case with our innocent civilians in Belgorod?" Medvedev, now deputy chairman of Russia's Security Council, said in a post on the X.

He was referring to an incident on Dec. 30 in the southern Russian border city, which the Kremlin says killed at least 20 people and injured 111 in what it claims was an "indiscriminate" Ukrainian cluster bomb attack.

"And I also hope that our archenemies, the impudent British understand that officially stationing their troops in Ukraine would mean declaration of war against our country," he added.

— Elliot Smith

Russia calls U.S. confiscation plan '21st century piracy'

Russian Foreign Ministry spokeswoman Maria Zakharova on Friday called the U.S. plan to confiscate up to $300 billion of frozen Russian assets "piracy of the 21st century," and vowed retaliation should the plan go ahead.

Zakharova told a news briefing that Washington was trying to create a "legal cover" to steal Russian assets in violation of international law, according to Reuters.

Bloomberg reported Wednesday that U.S. President Joe Biden's administration was considering legislation enabling the seizure of Russian assets and their repurposing toward rebuilding Ukraine after the war.

UK Prime Minister Sunak to visit Kyiv after announcing $3.2 billion Ukraine aid

U.K. Prime Minister Rishi Sunak will travel to Kyiv on Friday after his government announced that it will increase military funding for Ukraine to £2.5 billion ($3.19 billion) over the next financial year.

Armed Forces Minister James Heappey told BBC Breakfast on Friday that a key focus of this increased commitment to Ukraine is "the provision of all sorts of types of drones."

"They are drones that are being developed at pace, learning all of the lessons from what we've seen in Ukraine over the last two years," Heappey said.

"And we're confident that this enormous commitment from the U.K. public to Ukraine will allow us to deliver capabilities that will give Ukraine an advantage over the coming years."

— Elliot Smith

Ukraine says 64 combat clashes, 16 Russian rocket attacks on Thursday

Ukraine's armed forces said on Telegram Friday that 64 combat clashes took place the previous day, with Russian forces launching three airstrikes and 16 attacks from rocket salvo systems on Ukrainian positions and populated areas.

More than 130 settlements in the Chernihiv, Sumy, Kharkiv, Luhansk, Donetsk, Zaporizhzhia, Dnipropetrovsk, Kherson, and Mykolaiv regions came under artillery fire.

"As a result of Russian terrorist attacks, unfortunately, there are dead and wounded among the civilian population. Residential buildings, a professional lyceum and other civilian infrastructure were destroyed and damaged," the army said, according to a translation.

The Armed Forces of Ukraine claimed total Russian combat losses totaled 368,460 as of Friday morning. CNBC was not able to independently verify those claims.

— Elliot Smith

White House says U.S. assistance to Ukraine has 'ground to a halt'

U.S. military assistance to Ukraine has "ground to a halt," with Congress yet to authorize the emergency spending requested by President Joe Biden's administration in late October.

In a White House press briefing on Thursday, National Security Council Spokesperson John Kirby said Washington had "issued the last drawdown package that we had funding to support."

"And that's why it's critical that Congress move on that national security supplemental request and we get more funding. The assistance that we provided has now ground to a halt," he said.

"The attacks that the Russians are conducting are only increasing, and now, as I talked about earlier this week, they're using North Korean ballistic missiles to do their dirty work, so the need is acute right now, particularly in these winter months."

— Elliot Smith

Estonia PM pledges more Ukraine aid, says similar from others could help Kyiv win war

Estonian Prime Minister Kaja Kallas on Thursday announced a fresh 80 million euros ($87.5 million) in military assistance to Ukraine, and said Estonia would provide long-term assistance equaling 0.25% of its GDP over the next four years.

"If all the countries supporting Ukraine made a similar commitment, this would lead to a definite victory for Ukraine," Kallas said. 

She met with Ukrainian President Volodymyr Zelenskyy in the Estonian capital Tallinn.

A memorandum of understanding was signed in support of defense partnerships between the countries, including research and production of autonomous systems, and electronic warfare equipment, according to a release.

Zelenskyy is touring the Baltic states, which also includes Latvia and Lithuania. Located near Russia's northern border, the former Soviet states — all European Union members — are among Ukraine's staunchest allies.

— Jenni Reid

Cold snap in Ukraine affects maneuverability on both sides, UK says

A cold snap in Ukraine, with snow and freezing ground temperatures, is hampering operating conditions for both Russian and Ukrainian forces, the U.K. Ministry of Defense said Thursday.

"The worsening conditions will be compounded by shortened daylight hours making operating conditions difficult for both sides, which will have to rely on cold weather and night-vision equipment to operate," the ministry said on X, formerly known as Twitter.

Increased snow cover is also likely to be a limiting factor for maneuverability, the ministry said.

While frozen ground temperatures tend to allow for easier cross-country movement in January and February, the thaw that follows creates extremely muddy conditions, making it challenging for tanks and other military vehicles to move.

— Holly Ellyatt

Ukraine, Lithuania sign defense support agreement

Ukrainian President Volodymyr Zelenskyy said in a post on X, formerly Twitter, on Wednesday that he and Lithuanian President Gitanas Nauseda signed a new defense support agreement.

"I am grateful for Lithuania's new defense support that we have agreed upon—not only aid but also joint production—particularly of anti-drone equipment, which is critical at the frontline, as well as other areas of defense production. We signed relevant documents today," Zelenskyy said.

Zelenskyy also described weapons and other equipment as well as training for military personnel and Lithuania's role in the process of clearing mines in Ukraine as "sources of strength."

Earlier in the day, Zelenskyy said that he was making a surprise visit to Lithuania, Estonia and Latvia{=null}.

— Sophie Kiderlin