READ: House Democrats Release Draft Resolution On Impeachment Inquiry

Rep. Steve Scalise, the No. 2 House Republican, said Pelosi is "admitting guilt" by holding a vote.

Other panels are probing separate issues, including Trump's finances and abuses of White House security clearances.

Last week some Republicans - who argue there has been a lack of transparency in the proceedings - disrupted and delayed a hearing being held behind closed doors.

Tim Morrison, the NSC official who told Taylor that Ukraine's military aid was being held up to secure investigations into the role that former vice president Joe Biden's son Hunter had on Burisma's board, as well as a debunked conspiracy theory involving a Democratic National Committee that was hacked in 2016, is expected to testify in the impeachment inquiry on Thursday.

Trump took to Twitter on Tuesday to denounce the probe as a "sham", adding: "Read the call transcript and the impeachment hoax is over!"

A phone call between Ukrainian President Volodymyr Zelensky and Trump is at the heart of a whistleblower complaint.

Col Vindman said he was "concerned" by the call as he "did not think it was proper to demand that a foreign government investigate a USA citizen".

Those details about the president's potential political opponents were included in the whistleblower complaint, but Vindman, who was on the July 25 call, tried and failed to update those details on the rough transcript, he testified, sources told the Times. He writes, "It is similarly disgraceful that Trump is saying Lt. Col. Vindman is being political".

The eight-page document sets out a two-stage process for the next phase of the inquiry.

Rules Committee Chairman James McGovern of MA said the resolution provides "a clear path forward" as the House begins a public phase of the impeachment inquiry, which has largely been conducted behind closed doors.

"They don't accept that President Trump won the election". The Republican response to Vindman's testimony is already clear: They are smearing him as a Ukrainian spy. Trump last week called "Never Trump" Republicans "human scum". "Due process starts from the beginning".

On Monday night, Vindman's damning opening statement circulated among the public.

Vindman reported his concerns about the call to the NSC's lead counsel. At the direction of his superiors at the National Security Council, including John R. Bolton, then the national security adviser, Colonel Vindman drafted a memorandum in mid-August that sought to restart security aid that was being withheld from Ukraine, but Mr. Trump refused to sign it, according to documents reviewed by the Times.

Republicans mobilised to undercut Vindman's credibility, questioning his loyalty by noting he immigrated to the United States from the Soviet Union at the age of three, and suggesting he is part of an effort by the USA national security bureaucracy to undermine Trump. Trump alleges that Biden's son used his father's position to obtain huge profits from a Ukrainian gas company.

After playing a clip of Fox News host Laura Ingraham and her hosts attempting cast doubt on Vindman's loyalty for speaking to Ukrainians, Keilar explained that speaking to Ukrainians is quite literally Vindman's job as the director of European affairs at the National Security Council.

The White House is seen from the North entrance on December 22, 2018 in Washington, DC.

Alex Moe of NBC News tweeted Van Drew's statement earlier today.

President Trump joined the pile-on by claiming, without evidence, that Vindman is anti-Trump.

Some Trump allies, looking for ways to discredit Mr Vindman, questioned the colonel's loyalties because he was born in the region, but the line of attack was rejected by some Republicans, including Liz Cheney, who said it was "shameful" to criticise his patriotism. "This is a decorated American soldier, and he should be given the respect that his service to our country demands".

Trump and his supporters have taken other means to ensure that the cost to individuals who defy him is high.