Ukrainian President Volodymyr Zelenskyy has called on the US to provide his country with fighter jets, and criticised America for hesitating to supply them.
In a late night video message on Saturday, Zelenskyy said that "ping-pong" continued in discussions on who should deliver fighter planes and other defensive weapons to Ukraine.
Zelenskyy said Ukraine could not defend itself, or liberate cities like Mariupol, without tanks and combat aircraft.
"Ukraine can't shoot down Russian missiles with shotguns, machine guns, of which there are too many in the supplies. It's impossible to unblock Mariupol without a sufficient number of tanks, other armoured vehicles -- and especially without jets."
His comments come after Ukraine's foreign minister and defence minister met American officials and President Biden in Poland for talks about military assistance.
Zelenskyy said he had talked to Ukrainian forces defending Mariupol and urged Western partners to have at least "1% of their courage".
In his latest video address, the president also assailed Russian claims that Ukraine is trying to wipe out the use of the Russian language.
"You are doing everything so that our people themselves leave the Russian language, because the Russian language will now be associated only with you, with your explosions and murders," he added.