Senate Majority Leader Chuck Schumer arrived Friday in Ukraine in an effort to put pressure on his Republican opponents in Congress to unlock crucial aid as Russia's war enters its third year.
"We are here to show the Ukrainian people that America stands with them and will (continue) fighting to get the funding they so desperately need and deserve," Schumer said in a statement from the western Ukrainian city of Lviv.
"We will not stop fighting until we gain the aid."
Republican legislators in the House of Representatives have stalled the approval of $60 billion in new aid for Kyiv, with Ukrainian forces running low on supplies and Russia recently scoring a key battlefield gain.
"We are here to learn in granular detail about the armaments Ukraine so vitally needs and the consequences of the failure to deliver them -- the specific advantages Russia would gain if the arms are not delivered, and the advantages Ukraine would gain if the arms were delivered," said Schumer, who was accompanied by four Democratic senators.
The United States has provided tens of billions of dollars in military aid to Ukraine and is by far Kyiv's biggest donor.
But existing US funding has dried up, and former president Donald Trump's allies in the House have been stalling new assistance.
US President Joe Biden has urged Congress to quickly approve the additional funding, saying that "history is watching" and that abandoning Ukraine would be a gift to Putin.
Schumer echoed that statement, saying that "we are at an inflection point in history".
"We must make it clear to our friends and allies around the globe that the US does not back away from our responsibilities and allies," he said in his statement.
"If we fail to stand by our allies there will be severe political, diplomatic, economic, and military consequences that will significantly hurt the American people over the next decades."
Ukrainian President Volodymyr Zelensky on Friday made a fresh appeal to US lawmakers in an interview with Fox News, a channel widely viewed by American conservatives.
"Will Ukraine survive without Congress's support? Of course. But not all of us," Zelensky said in an interview near a front line in Ukraine.