The House Intelligence Committee subpoenaed acting White House Chief of Staff Mick Mulvaney Mick MulvaneyOn The Money: House panel pulls Powell into partisan battles | New York considers hiking taxes on the rich | Treasury: Trump's payroll tax deferral won't hurt Social Security Blockchain trade group names Mick Mulvaney to board Mick Mulvaney to start hedge fund MORE on Thursday evening to appear at a deposition as part of the impeachment inquiry Friday morning.

“Mr. Mulvaney has the opportunity to uphold his oath to the nation and constitution by testifying tomorrow under oath about matters of keen national importance,” an official working on the impeachment inquiry said late Thursday. “We hope Mr. Mulvaney does not hide behind the President’s ongoing efforts to conceal the truth and obstruct our investigation.”

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Mulvaney is unlikely to show up for the appearance despite the subpoena. The White House has refused to cooperate in the impeachment inquiry this far, accusing House Democrats of an unfair process and a partisan effort to overturn the results of the 2016 election.

Other current and former officials have evaded subpoenaed testimony, arguing they are immune from compelled congressional testimony as top advisers to the president.

Three House committees sent a letter to Mulvaney earlier this week requesting that he testify behind closed doors on Friday. White House counselor Kellyanne Conway Kellyanne Elizabeth ConwaySpecial counsel investigating DeVos for potential Hatch Act violation: report George and Kellyanne Conway honor Ginsburg Trump carries on with rally, unaware of Ginsburg's death MORE told reporters at the White House on Wednesday that Mulvaney was not expected to show up.

House investigators have conducted more than a dozen closed-door interviews with current and former officials since the impeachment inquiry was announced in late September. This week, Democrats began releasing hundreds of pages of transcripts of witness interviews that have illuminated concerns about the involvement of 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's personal attorney Rudy Giuliani Rudy GiulianiThe Hill's Campaign Report: GOP set to ask SCOTUS to limit mail-in voting CIA found Putin 'probably directing' campaign against Biden: report Democrats fear Russia interference could spoil bid to retake Senate MORE in the administration’s foreign policy toward Ukraine.

The interviews have also contributed to a body of evidence that the Trump administration tried to leverage a White House meeting and security assistance to Ukraine in order to press Kiev to pursue investigations sought by Giuliani and Trump. House Democrats have scheduled public hearings to begin next week.

Mulvaney, who headed the Office of Management and Budget before being tapped as Trump's acting chief of staff, is viewed as a key witness because of his involvement in the decision to withhold $400 million in security aid to Ukraine. That aid was eventually released.

At a White House briefing last month, Mulvaney indicated that the aid was contingent in part on Ukraine pursuing an investigation related to the 2016 hack of the Democratic National Committee server.

Mulvaney later walked back his remarks, saying there was no quid pro quo in the Trump administration’s dealings with Ukraine and blaming the media for misinterpreting his statement.

Trump has insisted that his call with Ukrainian President Volodymyr Zelensky, the event at the center of the inquiry, was "perfect" and that there was no quid pro quo in his dealings with Ukraine.