Ukrainian President Volodymyr Zelensky said on Sunday that 31,000 Ukrainian soldiers had been killed since Russia's full-scale invasion two years ago, giving the first official figure for more than a year.
Zelensky said his country's victory "depends" on Western support and that he was "sure" the United States would approve a critical package of military aid.
"Whether Ukraine will lose, whether it will be very difficult for us and whether there will be a large number of casualties depends on you, on our partners, on the Western world," Zelensky said.
He spoke at a press conference in Kyiv dedicated to the second anniversary of Russia's invasion at a time when Ukraine has been weakened by a shortage of ammunition and the blocking of US aid in Congress.
"There is hope for Congress, and I am sure that it is going to be positive, otherwise I do not understand the world we will start to live in," Zelensky said.
The aid has been blocked amid resistance from Republicans.
Ukraine has not put a number to its military losses since the end of 2022, when presidential aide Mykhailo Podolyak said 13,000 Ukrainian soldiers had been killed since the invasion on Feb. 24.
Battlefield casualties are a highly sensitive subject in a country trying to reform how it mobilises civilians into the army to regenerate its forces after last year's counteroffensive proved unable to break through Russian lines.
"Not 300,000 or 150,000, or whatever (Russian President Vladimir) Putin and his lying circle are saying. But each of these losses is a great loss for us," he added.
Both sides are believed to minimise deaths of troops.
A New York Times report in August cited U.S. officials as putting the Ukrainian death toll at close to 70,000. The same report said as many as 120,000 Russian troops had died during the war.
Asked if he would talk to Putin, Zelensky said: "Can you talk to a deaf person? Can you talk to a man who kills his opponents?"
Putin's main opponent Alexei Navalny died in an Arctic prison this month.
"He sees himself (in power) by 2030, we would like to finish with him sooner," Zelensky added, mocking an upcoming presidential election in Russia that is likely to extend Putin's long rule until 2030.
