House Democrats on Wednesday released the transcript of William Taylor's closed-door testimony in the impeachment probe into President Trump Donald John TrumpFederal prosecutor speaks out, says Barr 'has brought shame' on Justice Dept. Former Pence aide: White House staffers discussed Trump refusing to leave office Progressive group buys domain name of Trump's No. 1 Supreme Court pick MORE.

Taylor, the top U.S. diplomat in Ukraine, was the first official to testify that a quid pro quo existed, with the Trump administration withholding Ukrainian military aid while requesting that Ukraine launch politically motivated investigations into interference in the 2016 election and former Vice President Joe Biden Joe BidenFormer Pence aide: White House staffers discussed Trump refusing to leave office Progressive group buys domain name of Trump's No. 1 Supreme Court pick Bloomberg rolls out M ad buy to boost Biden in Florida MORE and his son Hunter.

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"That was my clear understanding, security assistance money would not come until the President committed to pursue the investigation," Taylor said in the testimony, referring to Ukrainian President Volodymyr Zelensky.

Taylor is also scheduled to testify publicly next week, as the impeachment probe enters its next phase. Democrats are releasing transcripts from the closed-door phase of their probe in batches this week.

Read Taylor's full testimony transcript here or below: