Secretary of State Mike Pompeo will make his first visit to Ukraine to “reaffirm” American support, according to his spokesperson, after the United States’ bipartisan backing for the country was rocked by allegations that President Donald Trump made an effort to pressure its new government into announcing investigations to favor him politically — an effort that has culminated in impeachment proceedings against him.

While senior State Department officials said strengthening U.S.-Ukrainian relations will be the focus of Pompeo’s one-day trip on Friday, impeachment and the lingering questions about Trump’s views on Ukraine will hang over his short time in Kyiv — as will the departure of the top U.S. diplomat.

Bill Taylor, a key witness in the impeachment hearings who’s been trashed by Trump, will depart his post one day before Pompeo arrives, according to two State Department sources. He testified about his concerns over Trump’s personal lawyer Rudy Giuliani and a campaign to have Ukrainian President Volodymyr Zelenskiy announce investigations into former Vice President Joe Biden, his son Hunter, and Hunter’s position on the board of Ukrainian energy company Burisma, as well as the debunked theory known as Crowdstrike. Named after the cyber security firm that first noted Russian cyber attacks in 2016, the theory posits that Ukraine, not Russia, was responsible for the election interference, working with the Democratic Party.

Taylor, who’s served as charge d’affaires since June, was limited by law to 210 days in his role, but his tenure would have expired next week — prompting questions of whether Pompeo forced him to depart early to avoid being seen with him.

A senior State Department official refused to comment on that Monday, saying the trip’s focus is “on our mission and our engagement with Ukraine.” They added that the U.S. embassy team is “terrific” and “incredibly dynamic.”

Trump has blasted Taylor, who Pompeo recruited for the role after he served as ambassador to Ukraine under George W. Bush, as a “Never Trumper.” Pompeo told reporters last month that he “always defend[s] State Department employees … the greatest diplomatic corps in the history of the world,” but he declined to comment specifically on Taylor or Marie Yovanovitch, the envoy to Ukraine that was recalled early by Trump.

More pressing than personnel, however, is the deep uncertainty over Trump’s support for Zelenskiy’s administration and whether the demand he made in that now infamous July 25 call is still on the table: Announce investigations into the Bidens and Crowdstrike, in exchange for an Oval Office meeting, a signal Zelenskiy wants to show that he has Trump’s backing.

The two presidents met on the sidelines of the United Nations in New York in September, but over eight months after his upset election, Zelenskiy hasn’t been invited to the White House. Instead, earlier this month, Trump welcomed Russian Foreign Minister Sergei Lavrov for a closed-door Oval Office meeting, with Pompeo and Lavrov calling for ways to improve relations despite the many disagreements.

The senior State Department official told ABC News that Lavrov’s visit was “a useful opportunity to talk about the Normandy format summit … and the Secretary was able to raise that and underscore our support for Ukraine.” The Normandy summit was a meeting on Dec. 9 between Russian President Vladimir Putin and Zelenskiy, along with France and Germany’s leaders, to restart the peace process between the two countries after nearly six years of Russian aggression against Ukraine.

The senior official deferred questions on when Zelenskiy would get a similar White House invite and whether those investigations were still conditions for an invitation to the White House. Pressed by reporters on whether Pompeo would raise the Bidens and Crowdstrike, they repeatedly deferred to other topics, especially Zelenskiy’s reform agenda that helped the political newcomer and former comedian win a commanding victory in April, along with his party in the July parliamentary elections.

“The Secretary’s agenda is very much focused on what we’re doing with Ukraine, the aid and assistance, the coordination, helping Ukraine follow through with its reforms, strengthening rule of law, creating a healthier investment climate, reforms in the security sector institutions, and … continuing to defend Ukraine’s freedom in the east, where there continues to be Russian aggressive behavior,” the official said.

Among that assistance is the $392 million of security assistance — for weapons, including sniper rifles and rocket-propelled grenade launchers, maritime security and secure communications — that Trump ordered withheld in June and released in September after pressure from lawmakers of both parties and the beginnings of a congressional investigation. The aid has been delivered to Kyiv, shortly after the Trump administration approved a new purchase of Javelin anti-tank missiles by Ukraine — a move former President Barack Obama never approved, arguing that his administration did not want to escalate the conflict.

The war, which has killed over 13,000 people, began in February 2014 with the use of Russian irregular forces and mercenaries crossing into eastern Ukrainian provinces to lead an uprising against Kyiv after pro-Western protesters toppled the government of Russian-backed oligarch Viktor Yanukovych that month. At the same time, Russian forces entered and occupied Crimea, the strategically important peninsula on the Black Sea, and held a referendum widely regarded as fraudulent to return it to Russian control.

U.S. and the European Union have since sanctioned Russia for its aggression and expelled it from the then G-8 summit. In addition, the U.S. has provided over $3 billion in assistance, including $1 billion of loans, to the new Ukrainian government, while the EU has provided more than €15 billion in assistance and loans.

That’s part of what alarms U.S. and Ukrainian officials about Trump’s calls for restoring relations with Russia, especially after he told ABC News during the 2016 campaign that he would look into recognizing Russian control of Crimea.

Contrary to that position, Pompeo issued the “Crimea Declaration” in July 2018, saying that the U.S. will never recognize Russia’s illegal annexation of the peninsula. Administration officials have consistently issued support for Ukraine’s full sovereignty and territorial integrity.

But Zelenskiy faces challenges in winning back that control. While Russia and Ukraine engaged in a prisoner swap earlier this month — and an additional 76 Ukrainian prisoners were freed by Russian-led separatists Sunday, per Zelenskiy’s office — Russia still controls Crimea and has pushed for Ukraine’s eastern provinces to gain a semi-independent status from Ukraine’s central government.

At the same time, Zelenskiy faces an uphill climb in implementing an extensive reform agenda, from monetary policy to the security sector, but especially in implementing greater rule of law. Parliament, which his party now has majority control of, passed reforms earlier this year, including ending parliamentary immunity and reforming and strengthening anti-corruption agencies and laws.

“Considerable amounts” of U.S. assistance have supported those efforts, according to the senior official, and Ukrainian officials “have gone out of their way to praise the U.S. assistance in those areas.”

But as Pompeo touts those efforts this week, it’s unclear whether Trump’s own efforts to skirt the rule of law in the country will have as much resonance.