US Senate Majority Leader Chuck Schumer is heading to Ukraine to try to reassure President Volodymyr Zelenskyy that Congress will deliver another round of US aid, even as a package that would provide $US60 billion to the war-torn country is stalled in the US House.

Schumer’s surprise trip comes at a perilous time for Ukraine. Zelenskyy has said that delays in aid from the US and other Western countries are creating an opening for Russia to make advances on the battlefield, with Ukrainian forces running dangerously low on ammunition and weaponry.

Lawmakers from both parties have travelled to Europe in the last week to promise the United States will not desert Ukraine and other European allies. Yet the path ahead is far from certain. The Senate passed a $95 billion package to aid Ukraine, Israel and Taiwan last week, but Republican House Speaker Mike Johnson has not yet put forward a plan for passing it in the House.

In an interview ahead of his trip, Schumer told The Associated Press he will tell Ukrainian officials that “we’re going to win this fight, and America is not abandoning them”.

“We are right at a vortex, a critical turning point in the whole West. And if we abandon Ukraine, the consequences for America are severe.”

The Senate passage of the aid package last week came after the collapse of a broader framework that would have combined the aid with changes to American border policies. The Senate quickly moved ahead with just the foreign aid portion, passing it on a 70-29 vote, with 22 Republicans in support.

But GOP opponents of aiding Ukraine are a vocal faction in the House, where Republicans have narrow control and former President Donald Trump, the front-runner for the GOP presidential nomination, holds more sway. Trump has opposed the aid package and urged Republicans to vote against it.

Schumer’s visit comes days after senators and House lawmakers from both parties travelled to the Munich Security Conference to try to reassure European leaders, including Zelenskyy, who are closely watching the US developments. The conference coincided with Ukraine withdrawing troops from the eastern city of Avdiivka after months of intense combat.

Johnson is caught between a wide swathe of his Republican members who support the Ukraine aid and a vocal faction on the right who strongly oppose it. Some House Republicans have threatened to try to remove him from his job if he puts the aid package up for a vote. He has said he ‘‘won’t be rushed’’ into a decision.

Republicans who oppose the aid say that the money is better spent in the US and that it should be paired with legislation to curtail record numbers of crossings at the southern border. They rejected the proposed Senate compromise on border policy, saying it was not tough enough, and some of them want to see the House try again to tackle that issue before moving to the national security package.

In the Senate, a group of Republicans opposed to the foreign aid kept the chamber open all night to rail against it before the final vote. Some of them echoed Russian President Vladimir Putin in calling for a negotiated end to the war.

Senator JD Vance, part of the increasingly isolationist wing of the GOP, travelled to the Munich conference to make his case. He countered Zelenskyy’s pleas by saying that additional money wouldn’t “fundamentally change the reality” on the ground.

“Can we send the level of weaponry we’ve sent for the last 18 months?” Vance asked. “We simply cannot. No matter how many cheques the US Congress writes, we are limited there.”

Schumer said opposition to the aid “may be the view of Donald Trump and some of the hard right zealots. But it is not the view of the American people, and I don’t think it’s the view of the majority of people in the House or Senate.”

He said he plans to tell Zelenskyy and other officials that he will push the House to act, and that “they shouldn’t give up and we’re not giving up”.

President Joe Biden has continued to tell Zelenskyy that he will get the aid to Ukraine. But he has expressed concerns about whether the House would be able to pass the aid before Russia takes more Ukrainian territory.

“The idea now when they are running out of ammunition that we’re going to walk away, I find it absurd,” Biden told reporters after speaking to Zelenskyy last weekend.

Schumer said he is “greatly worried” about what could happen if Congress doesn’t act.

“They’re hurting,” he said of Ukraine. “And I think by us being there, we’re giving them strength and giving them hope that America is still fighting for them.”

–AAP