Lt. Col. Alexander Vindman testified Tuesday that he believed 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 blocked military aid to Ukraine in an attempt to force Ukrainian President Volodymyr Zelensky to publicly announce an investigation into 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’s family, according to CNN.

Vindman said he believed there was a quid pro quo in place by July 10 after a meeting between American and Ukrainian officials. During the meeting, Vindman said Ambassador to the European Union Gordon Sondland told Ukrainian officials they needed to ensure “specific investigations in order to secure the meeting” with Trump.

The alleged quid pro quo came just two weeks before the July 25 call between Trump and Zelensky.

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In a subsequent meeting of U.S. officials, Vindman testified, "Sondland emphasized the importance that Ukraine deliver the investigations into the 2016 election, the Bidens, and Burisma," the natural gas company where Biden’s son served on the board.

Vindman said he was not convinced the president was personally holding up the $400 million in U.S. military aid until the next month, when then-national security adviser John Bolton John BoltonJudge appears skeptical of Bolton's defense of publishing book without White House approval Maximum pressure is keeping US troops in Iraq and Syria Woodward book trails Bolton, Mary Trump in first-week sales MORE asked him to prepare a decision memo recommending to Trump that he release the funds.

Following a meeting of administration officials on Aug. 16, at which Vindman was not present, he learned Trump was still holding up the aid, which suggested to him that Trump was still waiting for a public announcement of an investigation.

Rep. Lee Zeldin Lee ZeldinDCCC reserves new ad buys in competitive districts, adds new members to 'Red to Blue' program Overnight Defense: House panel probes Pompeo's convention speech | UN council rejects US demand to restore Iran sanctions | Court rules against Pentagon policy slowing expedited citizenship The Hill's 12:30 Report: Republicans conduct in-person convention roll call MORE (R-N.Y.), one of Trump’s most vocal defenders in the House, reportedly pressed Vidman on his past meetings with Ukrainian government officials and asked him why he had not complied with orders to pressure the nation to investigate the Bidens. Vindman responded that he considered the order improper, according to CNN, citing a source present at the deposition.

Zeldin told CNN the source’s description of the exchange was “100% untrue, and that's why you should be able to watch these depositions live.”

The Hill has reached out to the White House for comment.