Two current National Security Council staff members, Alexander Vindman and Tim Morrison, are scheduled to appear this week and would be the first White House employees to testify in the inquiry. "Sondland that his statements were inappropriate, that the request to investigate Biden and his son had nothing to do with national security, and that such investigations were not something the NSC was going to get involved in or push", Vindman says.
Even if the House impeaches Trump, he would face a trial in the Republican-controlled Senate, which for the moment seems unlikely to convict the president and force his ouster.
Vindman is scheduled to be deposed on Capitol Hill on Tuesday.
A draft of the resolution was expected ahead of Thursday's vote, but Pelosi said it would establish procedure for public hearings, authorize the disclosure of closed-door deposition transcripts and set forth "due process rights for the President and his Counsel".
An Army officer at the National Security Council says he raised concerns twice over the Trump administration's effort to have Ukraine investigate Democrats.
The inquiry is looking into Trump's call, in which he asked Zelenskiy for a "favor" - to investigate Democrats - that the Democrats say was a quid pro quo for military aid and could be an impeachable offense.
"I did not think it was proper to demand that a foreign government investigate a United States citizen, and I was anxious about the implications for the U.S. government's support of Ukraine", Vindman, an army officer and the top NSC official handling Ukraine, says in testimony posted Monday evening by the New York Times, which he is set to deliver to congressional investigators on Tuesday. William Taylor, the top U.S. diplomat in Ukraine, mentioned Morrison 15 times in his opening statement to investigators, which is considered the most damning to date.
Vindman says he communicated his concerns to the NSC's attorney at that time, concerned that such a partisan play would split Congress on Ukraine aid.
Alexander Vindman, director of European affairs on the National Security Council (NSC), has been called to testify behind closed doors by the House of Representatives Foreign Affairs, Intelligence and Oversight committees.
The measure is more likely to cross within the Democratic-controlled Home on condition that 228 Democrats, out of a complete 435 Home members, are on document supporting impeachment or an impeachment inquiry.
Senior Democratic aides said the resolution will be released on Wednesday, with a House vote on Thursday.
The argument advanced by Kupperman's lawyers turns on his status as a close adviser to the president and may not be available for other administration officials who are lower down the executive branch organization chart or who did not have regular contact with Trump.
Joe Biden said past year that while still in office in 2016, he threatened to withhold almost $2 billion in aid unless then-Ukrainian President Petro Poroshenko ousted one of the country's top prosecutors, Viktor Shokin.
"I did not think it was proper to demand that a foreign government investigate a USA citizen, and I was anxious about the implications for the US government's support of Ukraine", Vindman intends to tell lawmakers, according to a draft of his opening statement obtained by The Washington Post.
The White House has said it will not provide documents or witnesses to House investigators because it considered the impeachment inquiry unfair and illegitimate.
President Donald Trump talks to reporters before boarding Air Force One for a trip to Chicago to attend the International Association of Chiefs of Police Annual Conference and Exposition, Monday, Oct. 28, 2019, in Andrews Air Force Base, Md.
"The meeting proceeded well until the Ukrainians broached the subject of a meeting between the two presidents", Col Vindman said, noting that Ukraine saw this as "critically important" for maintaining USA support.