The chairmen of the three House committees leading Democrats' impeachment inquiry said Tuesday they will issue a subpoena to a key official that the State Department blocked from testifying.

Gordon Sondland, the U.S. ambassador to the European Union, was scheduled to appear for a deposition before the committees on Tuesday until the State Department moved early in the morning to prevent his testimony.

House Intelligence Committee Chairman Adam Schiff Adam Bennett SchiffSchiff to subpoena top DHS official, alleges whistleblower deposition is being stonewalled Schiff claims DHS is blocking whistleblower's access to records before testimony GOP lawmakers distance themselves from Trump comments on transfer of power MORE (D-Calif.), Foreign Affairs Committee Chairman Eliot Engel Eliot Lance EngelHouse panel halts contempt proceedings against Pompeo after documents turned over Engel subpoenas US global media chief Michael Pack The Hill's Morning Report - Sponsored by The Air Line Pilots Association - Pence lauds Harris as 'experienced debater'; Trump, Biden diverge over debate prep MORE (D-N.Y.) and Oversight and Reform Committee Chairman Elijah Cummings Elijah Eugene CummingsBlack GOP candidate accuses Behar of wearing black face in heated interview Overnight Health Care: US won't join global coronavirus vaccine initiative | Federal panel lays out initial priorities for COVID-19 vaccine distribution | NIH panel: 'Insufficient data' to show treatment touted by Trump works House Oversight Democrats to subpoena AbbVie in drug pricing probe MORE (D-Md.) said they would subsequently move to subpoena Sondland later Tuesday for testimony and documents.

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Schiff had told reporters Tuesday morning that Sondland also had messages on a personal device that the State Department is withholding from Congress.

“These actions appear to be part of the White House’s effort to obstruct the impeachment inquiry and to cover up 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 misconduct from Congress and the American people. Ambassador Sondland’s testimony and documents are vital, and that is precisely why the Administration is now blocking his testimony and withholding his documents," Schiff, Engel and Cummings said in a joint statement.

“We consider this interference to be obstruction of the impeachment inquiry. We will be issuing a subpoena to Ambassador Sondland for both his testimony and documents,” they said.

The State Department moved to block Sondland's testimony, just hours before he had been set to speak with lawmakers behind closed doors on Capitol Hill. According to the committee chairmen, the State Department left a voicemail at 12:30 a.m. informing Sondland and his counsel of the decision.

Sondland had already flown to Washington from Brussels for the deposition, according to his lawyer, who added that he is ready to testify "on short notice" when he's permitted to appear.

"Ambassador Sondland believes strongly that he acted at all times in the best interests of the United States, and he stands ready to answer the Committee’s questions fully and truthfully," Robert Luskin, Sondland's attorney, said in a statement.

President Trump defended the decision not to allow Sondland to testify.

"I would love to send Ambassador Sondland, a really good man and great American, to testify, but unfortunately he would be testifying before a totally compromised kangaroo court, where Republican’s rights have been taken away, and true facts are not allowed out for the public to see," Trump tweeted.

Kurt Volker Kurt VolkerGOP senators request details on Hunter Biden's travel for probe Yovanovitch retires from State Department: reports Live coverage: Senators enter second day of questions in impeachment trial MORE, the former special envoy to Ukraine, testified before the House Intelligence, Foreign Affairs, and Oversight committees last week and provided text messages from among himself, Sondland and William Taylor, a top official in the U.S. Embassy in Ukraine.

Sondland is shown in the messages rejecting concerns from Taylor that Trump wanted the Ukrainian government to launch 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 and the business dealings of his son, Hunter, in exchange for financial aid. Sondland is also shown suggesting that the diplomats take their conversations offline.

"As I said on the phone, I think it's crazy to withhold assistance for help with a political campaign," Taylor wrote in a Sept. 9 message.

Sondland replied: "Bill, I believe you are incorrect about President Trump's intentions."

"The president has been crystal clear no quid pro quo's of any kind. The president is trying to evaluate whether Ukraine is truly going to adopt the transparency and reforms that President Zelensky promised during his campaign. I suggest we stop the back and forth by text," Sondland wrote.

The text messages also showed that Sondland was involved in discussions to set up a White House meeting after the Ukrainian president issued a statement announcing an investigation.

"I think [Trump] really wants the deliverable," Sondland wrote.

The complaint filed by the intelligence community whistleblower that spurred the impeachment inquiry further alleges that Sondland attended meetings in Kiev with Volker, Ukrainian President Volodymyr Zelensky and other Ukrainian officials to discuss on how to "navigate" Trump's demands and the different messages they were receiving from "official U.S. channels on the one hand and from [Trump's personal lawyer Rudy] Giuliani on the other."

The House committees are set to hear testimony on Friday from Marie Yovanovitch, who served as U.S. ambassador to Ukraine until May, when the Trump administration recalled her from the post.

Updated at 12:21 p.m.