KYIV - When Ukrainian President Volodymyr Zelenskyy flew to Washington this week to plead for wartime aid, he found himself caught in a bitterly partisan U.S. domestic political dispute - again.

Zelenskyy is well-practiced in how to avoid taking sides in internal U.S. affairs - a survival skill he acquired four years ago when his attempts to secure a visit with then-President Donald Trump trapped him at the center of a historic impeachment inquiry.

But far more is at stake for Ukraine this time, and it will be far more difficult for him to appear neutral.

For weeks, the Biden administration and House Republicans have deadlocked over a package that includes some $60 billion for Ukraine, money that Kyiv says is vital to holding back Russian forces. Republicans, however, have demanded that the funds be tied to hard line border security and immigration measures.

Even Republicans who support Ukraine are game to delay the money as they seize the chance to push for tougher border policies. And some party hard-liners aligned with Trump - a longtime Ukraine skeptic - say they are against any further aid to Kyiv.

This has left Zelenskyy and Ukraine in a potentially perilous position, caught in a political grudge match between Democrats and Republicans as a U.S. presidential election heats up.

Zelenskyy’s instinct to stay out of the crossfire probably contributed to his last-minute cancellation of a virtual address to a House and Senate briefing on Ukraine this month. The meeting devolved into a shouting match over U.S. border policy, and several Republicans stormed out.

The Ukrainian president, an actor by profession, hoped his personal visit - and his star power - might drill home the urgency of his request and inspire bipartisan action. But opponents did not budge. Approving the money this year is now all but impossible - a development that now seems even more worrisome after European Union leaders failed to approve their own roughly $55 billion aid package for Ukraine on early Friday.

“I feel sorry for him,” a senior European diplomat posted to Washington said, speaking on the condition of anonymity to be frank about Zelenskyy’s visit. “It didn’t change anything. It can’t have been good for his spirit.”

Even so, Zelenskyy managed to stay somewhat above the fray.

“He doesn’t want to appear as being partisan and working hand in glove with Biden, even though they are because he’s the president,” said Alina Polyakova, president and CEO of the Center for European Policy Analysis, a Washington-based think tank.

Zelenskyy has hosted Biden and other senior U.S. officials in Kyiv, and in a recent NBC interview, the Ukrainian president said Trump - who has claimed he could end the war in a day - should also visit Kyiv.

“There was a desire here in Washington to use Ukraine as a political hot potato and for the administration in a certain way to use the issue against Republicans,” Polyakova said. “He was in such a difficult position . . . he showed a real understanding of ‘don’t get involved.’”

That understanding probably stems heavily from his “terrible” experience with the impeachment scandal in 2019, said Mykola Bielieskov, a research fellow at the National Institute for Strategic Studies in Kyiv, a think tank attached to the Ukrainian presidential office.

At that time, Zelenskyy was a little-known leader seeking better ties with Washington, urging Trump to attend his inauguration and flattering the former reality TV star by praising his campaign skills.

Now, Zelenskyy is a household name in the United States and much of the world. But his worry remains the same: Taking sides in U.S. politics could cost Ukraine help from its most powerful supporter, as its very existence as a state is threatened by Russia.

“I think he’s really fearful for Ukraine,” Bielieskov said, “to be used as an instrument of one party against the other.”

In July 2019, two months after Zelenskyy took office, Trump called the freshly elected Ukrainian president.

Zelenskyy, new to both his position and to politics, was eager for a visit to the White House that would lend him gravitas on the world stage and send a signal to Russia that Washington stood with Ukraine. It would also have helped him outshine his predecessor, Petro Poroshenko, who had a “drop-in” visit with Trump in the Oval Office but never a formal bilateral meeting.

On the call, Trump asked Zelenskyy for “a favor.” That included an investigation of Hunter Biden and help finding a Democratic National Committee computer server that U.S. officials said was hacked by Russian intelligence ahead of the 2016 president election.

It later emerged that it wasn’t only the Oval Office visit that depended on the outcome of that request. Trump, who had publicly praised Russian President Vladimir Putin, also ordered some $400 million in Ukrainian military aid to be withheld until Zelenskyy agreed. That led to Trump’s first impeachment.

For Zelenskyy, then an inexperienced politician with an aggressive neighbor already invading Ukrainian territory in the country’s east, the risks were enormous: He was trapped between the two U.S. political parties, knowing he would need to rely on whichever won the 2020 election.

“We were one step to catastrophe,” Bielieskov said. “He learned his lesson. He became more circumspect.”

“He doesn’t want Ukraine to be used as a vehicle of internal politics,” he said.

Zelenskyy has changed dramatically in the four years since - learning nearly fluent English that has allowed him to better connect with U.S. lawmakers and gaining widespread international respect after he chose to remain in Kyiv to face the Russian invasion.

He has also developed “a very keen awareness of the nuance and also how to approach U.S. political leaders,” Polyakova said. “He’s realized you have to be grateful and thankful and really paint a story of success and paint a story of how the U.S. has been critical [in that].”

Trump and Biden have had vastly different relations with Ukraine, but Kyiv’s goals have not changed. “The main foreign policy principle of Ukraine in relation to the United States - both then and now - is the preservation of bipartisan support for Ukraine in the United States,” said Volodymyr Fesenko, head of the Center for Political Studies, a Kyiv-based research group also known as Penta.

But now Zelenskyy is also facing criticism and questions over Ukraine’s largely stalled ground counteroffensive this spring - and is increasingly aware of how little time he has to secure the aid he needs.

Meanwhile, Ukraine’s domestic political rivalries are spilling into the open. Zelenskyy recently rejected his top general’s description of the war as a “stalemate,” while the mayor of Kyiv has accused the president of authoritarianism.

By the time he got to Washington this week, Zelenskyy “was calm, collected but understandably dispirited,” said a congressional aide who spoke on the condition of anonymity to talk openly about the visit. He was “right in the crosshairs of domestic politics,” the aide said.

After nearly two years of war and now the challenge of navigating U.S. infighting, Zelenskyy “just didn’t have that normal zest,” the aide said.

Ukraine relies on the United States for weapons to hold its front-line positions as well as air defenses that protect Ukrainian cities from constant bombardment by Russian missile and drones. While Zelenskyy was on the road this week, Ukraine shot down several missiles over Kyiv. At a news conference Thursday, Russian President Vladimir Putin insisted that his war aims had not changed and that Russia would win.

Michael Birnbaum in Washington contributed to this report.