Pompeo is denying the testimony of his former adviser - a highly respected longtime diplomat - at a time when State Department morale is plummeting over the secretary's failure to defend Yovanovich from Giuliani's smear campaign or to protect the department from being used to serve the President's political goals.
The impeachment inquiry centers around an effort led by Trump's personal lawyer, Rudy Giuliani, to use American diplomats to press the Ukrainian government into investigating the appointment of former Vice President Joe Biden's son to the board of a gas company and a debunked conspiracy theory that people there interfered in the 2016 USA presidential election.
Pompeo portrays the inquiry, which centers on President Donald Trump's attempt to link US military aid to Ukraine to a corruption probe of a political rival, as unworthy of his attention.
Hale, who arrived Wednesday morning to testify behind closed doors, will also say that the State Department anxious about the reaction from President Donald Trump's personal attorney Rudy Giuliani, also one of the strongest advocates for removing the ambassador.
In testimony released on Monday, McKinley said he resigned when Pompeo refused to come to the defense of Yovanovitch after details of Trump's negative comments about her to Ukraine's president became public. The transcript showed that Trump had disparaged Yovanovitch during the call, calling her "bad news".
After memorandum was released, McKinley testified, he pushed Pompeo to release a statement supporting Yovanovitch multiple times. On all three occasions, according to the transcript of his deposition, he said he did not get a response from Pompeo. "Not once, George, did Ambassador McKinley say something to me during that entire time period".
Pompeo never gave him a substantive response, McKinley told lawmakers in his October 16 appearance. "I haven't had the chance - it's a pretty busy world out there - I haven't had the chance to follow this".
McKinley "wasn't involved in the Ukraine file, so it's not surprising that when Ambassador Yovanovitch returned to the United States that he didn't raise that issue with me", Pompeo said Thursday. "In May, when that took place, he didn't say a thing to me".
"At the end of the day, Pompeo's audience is sitting in 1600 Pennsylvania and it's got to be hard when you see the president the vice president, the White House spokeswoman all attacking you and your leader does not speak up for you", Pifer said.
Yovanovitch denied those allegations in a sworn deposition and said she had been told by Deputy Secretary of State John Sullivan that she was being recalled because the president lost faith in her, even though Sullivan said he was not aware of her doing anything wrong.
Meanwhile, State Department Counselor T. Ulrich Brechbuhl, who was subpoenaed to appear before the impeachment panel, was on the plane with Pompeo, who departed early Wednesday morning for Germany.
Last month, Pompeo told ABC News that McKinley never said a "single thing" about Yovanovitch to him.