WATCH: Security analyst on Ukraine's withdrawal from Avdiivka

A former NATO official says Ukraine has "suffered a blow" as its troops withdraw from the town of Avdiivka. 

Jamie Shea focused on 'emerging security challenges' while working for the security alliance. He says Russia is clearly making gains, but Ukraine probably withdrew for strategic reasons. 

"It was only prudent that Ukraine order a tactical retreat before the Russians surrounded its forces," says Shea. "But certainly, the Russians seem to have the advantage going into the spring."

'Russia will probe for signs of weakness'

Avdiivka lies roughly 15 kilometers from Donetsk, a city controlled by Russia. Shea does not think it holds significant strategic value for Ukraine, but he's warned that it can't afford many more setbacks. 

"The key thing now is for the Ukrainians to fortify their lines," says Shea. "The front is still 1,500 kilometers. That's a big line to defend. And Russia will be probing along that front for further signs of weakness." 

Ukraine's army chief announced the withdrawal on the same day that President Volodymyr Zelenskiy addressed the Munich Security Summit. Zelenskiy suggested that troops withdrew from Avdiivka partly because they were running short of weapons.  

"Now, the military will replenish, they will wait for the relevant weapons," said Zelenskiy. "There simply weren't enough, simply aren't enough. Russia has long-range weapons, while we simply don't have enough."

Looking to the U.S.

Ukraine is hoping to secure more military funding from the United States. The U.S. Senate has approved a bill that would provide $60 billion, but the Republican-led House of Representatives has yet to vote on it. 

House Speaker Mike Johnson responded to the bill last week, saying Republicans wanted a package that included funding to boost security at the U.S. border with Mexico. "Any so-called national security supplemental legislation must recognize that national security begins at our own border," said Johnson. 

The White House says President Joe Biden called Zelenskiy on Saturday, assuring him that the U.S. will continue to support Ukraine. 

Zelenskiy visited France and Germany on Friday, signing accords with the leaders of both countries. German chancellor Olaf Scholtz pledged an extra $1.2 billion in aid. Scholtz had already promised to send $8.5 billion to Ukraine over the course of 2024. France has said it will offer up to $3.2 billion this year.  

The European Union has also promised more money, pledging over $50 billion earlier this month. But funding is not the only challenge facing Ukraine. 

"The big problem is not just committing the money," says Shea. "It's actually converting that into tanks and artillery shells that arrive on the battlefield."

New research by the Kiel Institute for the World Economy suggests Ukraine is waiting for funds long after it receives pledges from some allies. The institute says "the gap between EU commitments and allocations remains very large - $155 billion committed vs $83 billion allocated." 

It also warns that the EU would need to "double its current level and pace of arms assistance" if it aims to replace the support provided by the U.S.. 

Shea says European arms manufacturers will have to boost production in order to help Ukraine, but that process will take time. 

"Clearly, ramping up Europe's defense production won't happen overnight," says Shea. "So the trick going through this winter is how do they keep Ukraine alive and hold that line, before that money can be converted into real ammunition and real missiles." 

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