Ukraine's President Volodymyr Zelenskiy has asked the United States for more support as officials acknowledged troops were killed during a front-line ceremony.
Ukraine's President Volodymyr Zelenskiy has called on the United States to provide more funding to help his forces counter Russia and invited former US president Donald Trump to fly in to see the scale of the conflict for himself.
Zelenskiy said US soldiers could eventually be pulled into a greater European conflict with Russia if the US did not step up support.
"If Russia will kill all of us, they will attack NATO countries and you will send your sons and daughters (to fight)," Zelenskiy said according to a transcript of an interview with NBC.
US President Joe Biden, a Democrat, has pressed the US Congress to pass a $US106 billion ($A163 billion) supplemental spending bill, with the bulk of the money going to bolster Ukraine's defences and the remainder split among Israel, the Asia-Pacific and border enforcement.
The Republican-led US House of Representatives has instead put forward its own funding plan.
It passed a bill last week to provide $US14.3 billion in aid to Israel but did not include any increase in aid for Ukraine.
US Senator Chuck Schumer, majority leader of the Democratic-controlled Senate, said he would not bring the House bill to a vote and Biden has vowed to veto it.
In the interview airing on Sunday, Zelenskiy invited former US president Donald Trump, a Republican, to visit Ukraine and see the fallout of the conflict initiated by Russia's President Vladimir Putin in February 2022.
Trump, who is seeking re-election in 2024 and is the leading candidate for his party's presidential nomination, has been sharply critical of US support for Ukraine and has said he could end the war in 24 hours if re-elected.
"If he can come here, I will need... 24 minutes to explain to president Trump that he can't manage this war," Zelenskiy said.
"He can't bring peace because of Putin."
Meanwhile, officials in Kyiv have acknowledged that numerous soldiers were killed by a Russian attack during a controversial ceremony in the front-line region of Ukraine.
The soldiers were taking part in a ceremony in the Zaporizhzhia region to honour Artillery Day when Russian shells hit the area.
The internet portal Ukrainska Pravda reported more than 20 dead.
Defence Minister Rustem Umerov confirmed the "tragedy" but did not give any figures.
The authorities in the soldiers' home region of Zakarpattia, or Transcarpathia, organised three days of mourning on Sunday.
Umerov expressed his condolences to the relatives of the "fallen soldiers of the 128th Mountain Infantry Brigade Zakarpattia" on Facebook.
He did not give any details - not even the day.
The incident is said to have occurred on Friday.
"All the circumstances of what happened will be clarified," Umerov said.
"Our enemy is an insidious terrorist."
Relatives and friends would receive honest answers, he pledged.
The head of the Zakarpattia military administration, Viktor Mykyta, announced on Sunday that the "brothers" had been tragically killed.
In the coming days, state flags were to be lowered to half-mast and a minute's silence was to be held in the morning.
Posts on social networks sharply criticised the military leadership for allowing such a ceremony to take place in the front-line area.
Those responsible must be punished, Ukrainians demanded in comments.
According to reports, the authorities and the minister had only confirmed the incident after the information had been circulating on social networks and in the media for a long time.