Mike Pompeo will travel to Ukraine this week in a gesture of support for its government, ahead of Donald Trump’s impeachment trial in the Senate on charges that he sought to pressure Kyiv into investigating a political rival.

The secretary of state’s trip on Friday to see Volodymyr Zelenskiy, will mark the highest-level US visit since the Ukraine scandal erupted over the summer, when it emerged that Trump had withheld military aid and an Oval Office invitation to Zelenskiy until Zelenskiy announced an investigation into the former US vice-president Joe Biden, and his son, Hunter.

Trump also wanted the Ukrainian government to open an investigation into a conspiracy theory, already debunked by US intelligence, that the Democratic party had sought to hide emails in a server located in Ukraine.

A senior state department official said Pompeo’s visit would “underscore the strong and unwavering US support for Ukraine in the face of Russia’s aggression and also to discuss Ukraine’s progress in implementing the reforms necessary for Ukraine’s Euro-Atlantic integration”.

In a briefing to reporters to preview Pompeo’s trip – which will also take him to Belarus, Kazakhstan, Uzbekistan and Cyprus – state department officials repeatedly ignored questions related to impeachment.

They also refused comment on the departure – before Pompeo’s arrival in Kyiv – of the acting US ambassador, Bill Taylor, who provided testimony at Trump’s impeachment hearings about his concerns an Oval Office meeting for Zelenskiy, and nearly $400m in US military aid, were being used as leverage to procure investigations that would be damaging to Trump’s opponents in the 2020 election.

According to witness testimony and press reports, Trump was scathing in private about the Ukrainian government, declaring at one point: “They are all corrupt, they are all terrible people.”

State department officials did not refer to those remarks, but offered a much more positive assessment of Zelenskiy, who won elections in April.

“The Ukrainian president has undertaken a tremendous number of reform efforts, has shown real leadership, some very positive developments,” one official said, adding Zelenskiy “is living up to his commitments and campaign promises in terms of trying to deal with individual Ukrainians”.

Trump was impeached by the House of Representatives for abuse of power and obstruction of Congress on 18 December. He now faces trial in the Senate, possibly in January. However, there is still no agreement on how a Senate trial would be conducted.

According to testimony by several former and current administration officials, Pompeo was fully aware of the effort to put pressure on Zelenskiy, spearheaded by the president’s personal lawyer and fixer, Rudy Giuliani. Pompeo did nothing to stop a success effort by Giuliani had his Florida business associates to oust the former ambassador to Kyiv, Marie Yovanovich.

The Pompeo visit comes at a time when Zelenskiy is seeking to defuse the conflict with Russia in western Ukraine. Kyiv and Russian-backed separatists exchanged 200 prisoners over the weekend and Zelenskiy confirmed on Monday that his government had signed a five-year gas transit deal guaranteeing Russian supply to Europe.

Also on Monday, the White House confirmed that Trump had spoken to Vladimir Putin on Sunday, some 24 hours after the Kremlin had reported the call. A White House statement said that Putin had thanked Trump for US information that helped foil a potential holiday terrorist attack in Russia.

“Both presidents committed to continuing counterterrorism cooperation between the two countries,” the statement said. “The presidents also discussed the state of relations between the United States and Russia and future efforts to support effective arms control.”