KYIV, Ukraine — Secretary of State Mike Pompeo returned to the country at the epicenter of President Trump's impeachment trial Thursday in a visit to Ukraine that presents both risks and opportunities for an administration eager to prove the president's innocence.

As lawmakers in Washington deliberate Trump’s fate, Pompeo will be greeted by a parade of senior Ukrainian officials desperate to project unity with an administration it relies on for military support against pro-Russian separatists.

When Ukrainian President Volodymyr Zelensky appears with Pompeo before cameras on Friday, White House officials hope the former comedian will reiterate a message that has become central to Trump’s defense: The president never pressured Ukraine to investigate Trump’s political rivals.

By simply repeating that line, Zelensky will be giving Pompeo a valuable deliverable at a time when some Senate Republicans are expressing unease about the impeachment process and pushing for witnesses to appear before the upper chamber.

A top aide to Zelensky who is angling to become his new chief of staff, Andriy Yermak, has urged his boss to embrace a pro-Trump line for the sake of his embattled country, according to diplomats familiar with the deliberations.

“From the Ukrainian point of view, they just want a joint presser with the secretary of state saying the U.S. supports Ukraine in its war with Russia,” said Angela Stent, a Europe and Russia scholar at Georgetown University. “I’m sure Zelensky will also say what he’s said before: He didn’t feel pressured to investigate the Bidens.”

But the visit also presents risks for Pompeo, the president’s closest adviser, who continues to face criticism inside and outside the State Department for overseeing the ouster of theambassador to Ukraine, Marie Yovanovitch.

Before landing in Kyiv, the capital, Pompeo told reporters his message to U.S. diplomats in Ukraine will be to “tell them how much we love them, appreciate them, appreciate their family members and their sacrifice.”

“Talk about the important work that the United States and Ukraine will continue to do together to fight corruption inside of that country,” he said aboard his plane Wednesday.

The nation’s top diplomat will be setting foot in the U.S. Embassy on Friday, home to some officials who expressed concern and alarm at the halt of U.S. military assistance to Ukraine last year, the lack of a White House meeting for Zelensky and alleged repeated efforts to force Ukraine to investigate former vice president Joe Biden.

David Holmes, a senior diplomat at the embassy, testified in November that he overheard Trump on a phone call inquiring about the Biden investigations in an account that Trump publicly denied. Holmes also corroborated other officials’ claims that a White House meeting with Trump was contingent on a Ukraine investigation into Biden and the Ukrainian energy company his son used to work for. It “was made clear that some action on a Burisma/Biden investigation was a precondition for an Oval Office meeting,” Holmes said.

It is unclear whether Pompeo will interact with Holmes during his embassy visit, but he is expected to hold a closed-door question-and-answer session with diplomats there.

One prominent impeachment witness who won’t be present is William B. Taylor Jr., the former top diplomat to Kyiv who stepped down earlier this month. Taylor sharply criticized the Trump administration’s Ukraine policy last year as “crazy” and extortionate, and he hasn’t gone into retirement quietly. He took direct aim at Pompeo in a New York Times column Sunday for purportedly asking a reporter if she thinks any Americans “care” about Ukraine.

“The answer should be yes,” Taylor wrote. “Ukraine is defending itself and the West against Russian attack. If Ukraine succeeds, we succeed.”

Besides confronting his own diplomats, Pompeo is likely to face questions from reporters about Ukraine — a topic that has elicited angry responses from him and even controversy.

Last week, Pompeo allegedly lashed out at NPR host Mary Louise Kelly in an expletive-fueled off-microphone rant after an interview in which she questioned his role in Trump’s Ukraine policy. In particular, Kelly asked if Pompeo owed Yovanovitch an apology for failing to defend her when the president pushed her out.

“He was not happy to have been questioned about Ukraine,” Kelly later said. “He asked, ‘Do you think Americans care about Ukraine?’ He used the f-word in that sentence and many others.”

Yovanovitch, a career diplomat respected within the department, accused Trump’s personal attorney Rudolph W. Giuliani of waging a smear campaign against her because her anti-corruption efforts threatened the business interests of Giuliani’s clients.

After his NPR interview, Pompeo issued a statement accusing Kelly of lying about what topics the interview would include and breaking a promise to keep the “post-interview conversation off the record.”

On the plane, Pompeo didn’t deny asking her about whether Americans care about Ukraine, but he pushed back at the idea that he thought they did not. “Of course the American people care about the people of Ukraine,” he said.

Kelly said she notified Pompeo’s staff that she would ask questions about Ukraine, a claim subsequently corroborated in emails between Kelly and his staff, and said she never agreed to have the post-interview conversation off the record.

The dust-up continued into this week when the State Department barred another NPR reporter, Michele Kelemen, from traveling with Pompeo on his trip. Pompeo told reporters on his plane that he did Kelly “the favor of granting her an interview,” but suggested she did not conduct it “straight down the middle.”

Whether Pompeo can avoid another blowup with reporters during his stay is unclear. But his Ukrainian counterparts are likely to be compliant and welcoming, said Andrew Weiss, a Russia scholar at the Carnegie Endowment for International Peace.

“The Ukrainians are in a horrible position,” Weiss said. “They have zero interest in directly antagonizing the Trump administration and, like the rest of the world, have to deal with the U.S. government that’s in place.”

Desmond Butler in Washington contributed to this report.