House Democrat leaders on Tuesday subpoenaed Gordon Sondland, the U.S. ambassador to the European Union, to testify at a deposition and hand over documents related to their impeachment investigation into President Donald Trump.

The subpoena came hours after the Trump administration ordered Sondland not to appear before a scheduled deposition with the Democrat-led panels conducting the impeachment inquiry.

The Associated Press reports:

House Democrats have subpoenaed Gordon Sondland, the U.S. European Union ambassador, after he failed to show up at a scheduled closed-door deposition Tuesday morning. The deposition was scheduled as part of House Democrats’ impeachment inquiry into President Donald Trump’s dealings with Ukraine. Sondland was an intermediary as Trump appealed to Ukrainian President Volodymyr Zelenskiy to investigate political rival Joe Biden and his family. Three House committees are demanding that Sondland appear at a deposition Oct. 16. They are also demanding that he produce documents, including communications from his personal device that have been turned over to the State Department but not to Congress.

Rep. Adam Schiff (D-CA), the chairman of the House Intelligence Committee, deemed the decision to prevent Sondland from testifying as “strong evidence of obstruction” by Trump.

In a statement, Jim McDermott, Sondland’s attorney, explained:

Ambassador Sondland had previously agreed to appear voluntarily today, without the need for a subpoena, in order to answer the committee’s questions on an expedited basis. As the sitting U.S. Ambassador to the EU and employee of the State Department, Ambassador Sondland is required to follow the department’s direction.

Sondland was “profoundly disappointed” he was unable to testify Tuesday but is willing to appear on short notice if permitted by the Trump administration, his lawyer added.

The Democrat-led House Committees on Oversight and Reform, Intelligence, and Foreign Affairs are leading the impeachment probe.

In a joint statement issued Tuesday, the chairmen of the House panels vowed to subpoena Sondland.

“We will be issuing subpoena to Ambassador Sondland for both his testimony and documents,” they declared.

A July 25 phone call between Trump and Ukraine President Volodymyr Zelensky ultimately triggered the impeachment probe. An intelligence community “whistleblower” filed a complaint alleging Trump pressured Zelensky on the phone call to investigate allegations of corruption against Joe Biden and his son.

Trump threatened to withhold aid if Ukraine did not play ball, the “whistleblower” claimed.

Sondland has contradicted the quid pro quo claim at the center of the impeachment inquiry. In a text message, the top diplomat clearly said there was “no quid pro quo of any kind” between Trump and Zelensky.

Last week, former U.S. special envoy to Ukraine Kurt Volker provided a series of texts to the House committees.

In written testimony, Volker described the communication exchanges as evidence that the Trump administration did not bully Ukraine into investigating Biden or his son.

House Democrats, nevertheless, leaked a “subset” of the texts to fuel their impeachment effort.

The Democrats used the texts to argue the complete opposite of what Volker testified, saying the communication exchange proves Trump made a quid pro quo offer.

Republicans are calling on the House Democrats to release the full transcript of Volker’s testimony.

On Tuesday, Rep. Mark Meadows (R-NC) said making the transcript public would “exonerate” Trump. Meadows witnessed the more than eight hours of testimony provided by Volker.

The impeachment inquiry proceedings are akin to a “kangaroo court” led by House Democrats who have cherry-picked and mischaracterized evidence, Republican congressmen argued Tuesday.

Rep. Lee Zeldin (R-NY), a member of the House Foreign Affairs Committee, noted that the proceedings fall outside the recognized standards of previous impeachment efforts.

House Democrats subpoenaed Sondland on the heels of a White House letter to House Democrats announcing that Trump would not cooperate with the impeachment inquiry.

Trump and members of his administration “cannot participate in your partisan and unconstitutional inquiry under these circumstances,” White House Counsel Pat Cipollone declared in the letter.

Rep. Jim Jordan (R-OH), the top Republican on the House Intelligence Committee, said he understands the White House decision not to allow Sondland to testify.

“The reason why the State Department decided not to have Amb. Sondland here today is based on the unfair and partisan process that Mr. Schiff has been running,” he told reporters Tuesday.

The White House letter said the impeachment probe is akin to an effort “seeking to overturn the results of the 2016 election.”