That might damage Trump, though some of his supporters say the impeachment drive could actually boost his re-election chances by showing him at loggerheads with Washington-based political foes.
"It's very clear that Mr. Pompeo's need to be close to President Trump and support him in every way has caused him to give up the integrity that I think is an essential element to being a successful leader", the former diplomat said.
Democrats say that's an improper quid pro quo.
Recently published testimony by the US Ambassador to the European Union Gordon Sondland has added even more controversy to an ongoing impeachment inquiry against US President Donald Trump, alleging that US military aid to Ukraine could indeed have been dependent on an investigation of Joe Biden's involvement in the country's internal affairs.
Sondland submitted the supplemental testimony on Monday after testimony by other officials, including Bill Taylor, the top United States diplomat at the embassy in Kyiv.
Also scheduled to testify publicly next week are former U.S. ambassador to Ukraine Marie Yovanovitch and career state department official George Kent. The people familiar with the matter were not authorized to discuss Hale's appearance publicly and spoke on condition of anonymity.
House Intelligence Committee Chairman Adam Schiff, who is leading the impeachment investigation, said the committee would hear from Taylor, career department official George Kent and former U.S. Ambassador to Ukraine Marie Yovanovitch in hearings next Wednesday and Friday.
"This is about more than just one call", Mr Schiff wrote in an op-ed in USA Today. If not, Giuliani said, according to the testimony, it would show Ukraine was not serious.
Kurt Volker, a Republican whom Mr. Trump's administration appointed as special envoy to Ukraine, testified that the allegations Mr. Trump wanted investigated about Mr. Biden were groundless and that their Ukrainian source was not credible.
"Ambassador Bolton was not interested in having - did not want to have the call because he thought it was going to be a disaster", Taylor testified. She detailed efforts by Giuliani and other Trump allies to push her out of Ukraine, testifying that a senior Ukrainian official told her that "I really needed to watch my back".
Democrats cost that Trump tried to stress Ukraine into digging up dust on the Bidens by withholding about $400 million in navy help. Transcript of the call as released by the White House apparently eliminates some significant narrative in the call.
They will testify on November 13 and 15, said Adam Schiff, the committee's Democratic chairman who wrote on Twitter that there was "More to come".