The president of Ukraine could have been forgiven for hoping President Donald Trump would back his fight against endemic corruption, and support his country in its grinding war against Russia-sponsored separatists.

Instead, during a July phone call, Volodymyr Zelenskiy was boxed into a Catch-22 by Trump, whose requests ran counter to years of U.S. foreign policy in the region.

That phone call now forms the basis of an impeachment inquiry against the U.S. president by House Democrats.

It also worries activists and experts, who say declassified details of the call mark a setback for pro-West reformers in the country — raising questions about the future of U.S.-Ukraine relations under the Trump administration.

"There's a certain feeling of injustice," said Orysia Lutsevych, a research fellow on Ukraine at the Chatham House think tank in London.

"The strategic partnership between Ukraine and the United States was always to make sure that Ukraine carries out reforms, that it is able to deter Russia, and has a rule-based government," she said. "But here, in this conversation between Trump and Zelenskiy, there was hardly any discussion about Russia, nor about the need for Ukraine to really build an independent judiciary."

"Quite the opposite: Trump wanted President Zelenskiy to use the judiciary for U.S. domestic politics," Lutsevych said.

A declassified whistleblower complaint alleges Trump pressured Zelenskiy to dig dirt on Democratic presidential candidate Joe Biden and his son Hunter in exchange for U.S. military aid.

Vice President Joe Biden and his son Hunter Biden attend an NCAA basketball game between Georgetown University and Duke University in Washington. Jonathan Ernst / Reuters file

A memo from the call has dismayed Ukrainian anti-corruption activists, who have devoted their lives to trying to rid politics of backroom deal-making between officials and business people.

Daria Kaleniuk said she was astonished to see the very tactics Washington has historically decried being deployed by its current president.

"This is exactly what we tried to change in Ukraine for the last five years," said Kaleniuk, who is executive director of Ukraine’s nongovernmental Anti-Corruption Action Centre.

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Transparency "is the cornerstone of Ukraine's anti-corruption reforms, which were reinforced for many years by the United States," she said. "And now the president of the United States is [acting] quite contrary to what we were actually trying to achieve."

The U.S. helped Ukraine establish its Anti-Corruption Bureau, which started work this year and whose officers were trained by the FBI.

Polls say reforms on this issue are at the top of the public's wish list. But Ukraine is still rated as having Europe's highest levels of perceived corruption, according to the watchdog Transparency International.

The International Monetary Fund said last week that "tangible results have yet to be achieved" in fighting "pervasive corruption."

The declassified call memo presents a "Catch-22" for Zelenskiy, who "can neither do what is being asked, nor say 'no' to the president of the United States," Lutsevych said.

The Ukrainian leader has promised to stamp out corruption, but he must still work with the U.S. because it's one of his main international backers.

Details of the call, which Zelenskiy will not have expected to be made public, shows him agreeing with Trump's criticisms of European leaders, such as Germany's Angela Merkel.

"Yes, you are absolutely right, not only 100 percent but 1,000 percent," he said.

Zelenskiy told reporters Monday, "We are an independent country. We are not following any commands. We have only one command: to serve Ukraine."

The Ukrainian leader also mentioned on the call his desire to buy U.S. anti-tank missiles. Trump replies with a request for "a favor" — look into a long-discredited conspiracy about Russia's 2016 hacking of the Democratic National Committee.

"The reply from President Trump was nothing about war, or about Javelins or about Russian aggression. It was something about national politics in the United States," Kaleniuk said, referring to the Javelin anti-tank missiles Ukraine wants to buy from the U.S.

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"For many years, the U.S. was the key partner in facing this aggression, but now it looks like we're being dragged into national political battle in the U.S. where ... we're forced to pick sides," she said.

The U.S. has given Ukraine $1.5 billion in security assistance since 2014, when the conflict with the pro-Moscow fighters began. More than 13,000 people have been killed since then.

Days before his call with Zelenskiy, the Trump administration froze almost $400 million in military aid to Ukraine. It released that hold just before Democrats in Congress revealed the existence of the whistleblower complaint.

Some believe that the intense focus on the issue might actually help Ukraine.

"A lot of people will now be watching the new prosecutor general," Lutsevych said, referring to Zelenskiy's recent appointment to the role. "This will put an extra magnifying glass on the whole thing."

"I think now the information is public, about the possible attempts to pressure Ukraine, the aid will flow," she added. "Any risk to military or technical assistance would be viewed as a punishment, not blackmail."