Ukraine's military wants to mobilise up to 500,000 extra people, President Volodymyr Zelensky has revealed, as the war with Russia nears a two-year mark.
At a news conference in Kyiv, he said his commanders were seeking "450,000-500,000 individuals", admitting this was a "sensitive" and costly issue.
He said he needed more details before backing the move, hinting that 500,000 soldiers were already on the front.
His comments come in the wake of aid setbacks from the US and the EU.
Republicans in the US Congress first blocked a $60bn (£47bn) military package for Ukraine earlier this month.
That was followed by Hungary's blocking of the EU's €50bn ($55bn; £43bn) financial aid deal last week. EU leaders, however, said Ukraine would not be left without support.
Ukraine is facing an ammunition shortage as it continues to fight occupying Russian forces, following Moscow's full-scale invasion in February 2022.
Kyiv's counter-offensive ground to a halt at the start of winter and there are fears that the Russians could simply outgun Ukraine.
Olena Zelenska, Ukraine's first lady, warned in a BBC interview earlier this month that Ukrainians were in "mortal danger" of being left to die without further Western support.
Russia President Vladimir Putin said this week that Moscow would continue its invasion, vowing that all his goals would be achieved.
The Kremlin leader also said that 617,000 Russian soldiers were now being deployed for what Moscow describes as a "special military operation". But he admitted that the armed forces had problems with air defence systems and communication, and needed to increase the production of drones.
President Zelensky's end-of-year news conference was held in the Ukrainian capital on Tuesday, with the time and venue being kept secret from the general public. Invited Ukrainian and foreign media had been given the details in their confirmation letters.
Appearing in his trademark military-style clothes, the Ukrainian leader was asked a wide range of questions during the two-hour event.
He revealed that Ukraine's top military commanders had "proposed to mobilise an additional 450,000-500,000 individuals" for the country's war effort.
He said this was a "very serious number" and he needed more in-depth discussion before committing to the plan.
"I need specifics: what will happen to the million-strong army of Ukraine, what will happen to those guys who have been defending our state for two years? We have issues of rotation and holidays. It should be a comprehensive plan."
But he ruled out any proposals to mobilise women.
When asked by the BBC's Jessica Parker about whether Ukraine could be on the cusp of starting to lose the war, Mr Zelensky was firm. "No," was the answer.
It's the answer you would expect, but he's not alone in expressing this kind of determination, our correspondent in Kyiv says. Many people she has met will not countenance anything other than beating back their Russian invaders, she adds.
During the briefing, Mr Zelensky also said that:
-Ukraine would be able to produce a million drones in 2024
-He had "working relations" with Ukraine's top military commander Valeriy Zaluzhnyi, playing down reports of a rift between the pair
-Peace talks with Russia were not currently feasible, stressing that he would seek to restore in full Ukraine's internationally recognised borders, including Crimea
During the whole event, the Ukrainian president sought to strike a confident note - but sometimes he appeared to be tense and tetchy when pressed over reports of corruption among Ukrainian government officials and lawmakers.