Ukrainian President Volodymyr Zelenskyy has made his second visit to Washington, DC, since Russian forces launched a full-scale invasion of his country.

But unlike in his first trip to the United States Capitol, Zelenskyy faced a congress less inclined to back the war effort with large aid packages, despite pledges from top Democrats to “stand behind” Ukraine.

In brief public remarks before the White House Cabinet on Thursday, Zelenksyy struck a note of gratitude, calling his negotiations in Washington “productive” and “strong”.

“Thank you for all these 575 days,” he said, referencing the length of time since the Russians invaded in February 2022.

“Thanks to the American people, all these days they are together with us, with Ukrainians, with ordinary people, all of us.”

He also highlighted new military assistance, worth $128m, announced by US President Joe Biden on Thursday.

“It has exactly what our soldiers need now,” he said, calling it a “very powerful package”.

Biden, a Democrat, used his presidential “drawdown authority” to authorise the aid, as further funds for Ukraine prove to be a sticking point in the US Congress.

“Today, I approved the next tranche of US security assistance to Ukraine, including more artillery, more ammunition, more anti-tank weapons,” he said. “And next week, the first US Abrams tanks will be delivered to Ukraine.”

The Cabinet meeting culminates a whirlwind charm offensive from the Ukrainian president, who travelled to New York earlier this week to rally support among world leaders at the United Nations.

But as Zelenskyy faced US leaders on Thursday, the stakes were particularly high.

Since the full-scale Russian invasion began in 2022, the US has committed more money than any single country to aid Ukraine, with much of that support taking the form of military assistance.

The US Congress itself has approved aid amounting to over $113bn. But the last time Congress voted on an aid package was in December – and control of the House of Representatives has since switched hands, from Democrats to Republicans.

Nevertheless, Biden has called on Congress to approve an additional $24bn for Ukraine aid, a request that some Republicans, particularly on the far right, have baulked at.

Some have called instead to slash funding for Ukraine, in favour of domestic priorities and limited government spending.

That perspective was on full display on Thursday, as Zelenskyy toured Capitol Hill.

US media reported that House Majority Leader Kevin McCarthy refused Zelenskyy’s request to address a joint session of Congress during his visit, as he had last December.

And while the Ukrainian leader was meeting with lawmakers on both sides of the aisle, 28 Republican Congress members signed and published a letter on Thursday opposing additional expenditures for Ukraine.

The US Congress is facing a September 30 deadline to pass budget legislation or face a government shutdown.

“The American people deserve to know what their money has gone to,” the 28 Republicans wrote. “How is the counteroffensive going? Are the Ukrainians any closer to victory than they were 6 months ago? What is our strategy, and what is the president’s exit plan?”

They added it would be “an absurd abdication of congressional responsibility” to grant President Biden’s request for more aid without answers first.

Al Jazeera correspondent Kimberly Halkett said the contrast to Zelenskyy’s first wartime appearance in Washington, DC, last December was stark.

“There is a lot more pushback on Capitol Hill than Volodymyr Zelenskyy is used to,” she said from outside the White House.

“Initially, he had received a warm welcome, bipartisan support in terms of approvals for funding for Ukraine’s defence and standing ovations all around. But this time there have been questions about how that money will be spent, where the past money has gone, and even whether the US can afford it.”

She warned that “war fatigue” among the US public would be an ongoing hurdle to Zelenskyy’s cause.

Still, Congressional Democrats rallied in support of Ukraine spending, echoing the party’s commitment to “stand behind” the war-torn country.

“This is a struggle between Ukraine and Russia,” House Minority Leader Hakeem Jeffries said in his weekly press briefing on Thursday.

“But it is also a struggle on the global stage between democracy and autocracy, between freedom and tyranny, between truth and propaganda, between good and evil. And it’s important for us to stand behind Ukraine until victory is won.”

Biden echoed those sentiments later at the White House Cabinet meeting.

“The entire world has a stake in making sure that no nation, no aggressor, is allowed to take a neighbour’s territory by force. The American people will never waver in their commitment to those values,” he said.

As Biden shook hands with Zelenskyy and prepared to leave the Cabinet meeting, a reporter shouted from the sidelines to ask whether the Democrat believed the US Congress would ultimately pass the requested aid for Ukraine.

Biden paused before responding. “I’m counting on the good judgement of the United States Congress,” he said. “There’s no alternative.”