Ukrainian President Volodymyr Zelenskyy warned allies Saturday that an “artificial deficit” of weapons for his country risks giving Russia breathing space, hours after his military chief said he was withdrawing troops from the eastern city of Avdiivka.

Zelenskyy spoke to the Munich Security Conference, an annual gathering of security and foreign policy officials. Ukraine is back on the defensive against Russia in the nearly 2-year-old war, hindered by low ammunition supplies and a shortage of personnel.

“Ukrainians have proven that we can force Russia to retreat,” he said. “We can get our land back, and (Russian President Vladimir) Putin can lose, and this has already happened more than once on the battlefield."

"Our actions are limited only by the sufficiency and length of range of our strength,” he added, pointing to the situation in Avdiivka. Ukrainian commander Col Gen Oleksandr Syrskyi said early Saturday that he was withdrawing troops from the city, where outnumbered defenders battled a Russian assault for four months, to avoid encirclement and save soldiers' lives.

“Dear friends, unfortunately keeping Ukraine in the artificial deficit of weapons, particularly in deficit of artillery and long-range capabilities, allows Putin to adapt to the current intensity of the war,” Zelenskyy said. “The self-weakening of democracy over time undermines our joint results.”

The president said that the troop withdrawal was “a correct decision” and emphasised the priority of saving Ukrainian soldiers' lives. He suggested that Russia has achieved little, adding that it has been attacking Avdiivka “with all the power that they had” since October and lost thousands of soldiers — “that's what Russia has achieved. It's a depletion of their army”.

“We're just waiting for weapons that we're short of,” he added, pointing to a lack of long-range weapons. “That's why our weapon today is our soldiers, our people.”

Zelenskyy on Friday went to Berlin and Paris, where he signed long-term bilateral security agreements with Germany and France, following a similar agreement with Britain last month.

Ukraine's European allies are appealing to the US Congress to approve a package that includes aid for Ukraine, $60 billion that would go largely to US defence entities to manufacture missiles, munitions and other military hardware for the battlefields in Ukraine. The package faces resistance from House Republicans.

Zelenskyy said Saturday that the US “did a lot for us” and thanked Washington for bipartisan support. He said he planned to meet US senators in Munich on Saturday. They “have to understand (that) only in unity we can win (against) Russia,” he said.

Asked whether it would be a good idea to invite former US president and 2024 presidential hopeful Donald Trump to Kyiv, Zelenskyy replied: “I invited publicly, but it depends on his wishes.”

“If...he will come, I'm ready even to go with him to the front line,” he added.

Zelenskyy argued that “among us, there is no one for whom the ongoing war in Europe does not pose a threat”.

“Please do not ask Ukraine when the war will end,” he said. “Ask yourself why is Putin still able to continue it.