New Ambassador of the United States to the European Union Gordon Sondland is talking to media prior an EU Energy Council, on July 12, 2018, in the Berlaymont, the EU Commission headquarters.

Gordon Sondland, the U.S. ambassador to the European Union, will appear for a deposition before House committees as part of the impeachment inquiry in spite of an attempt by the Trump administration to block his testimony.

"After consultation with Committee Staff, his testimony is now scheduled for Thursday, October 17," Sondland's lawyer, Robert Luskin, said in a statement to NBC News on Friday.

"Notwithstanding the State Department's current direction to not testify, Ambassador Sondland will honor the Committees' subpoena, and he looks forward to testifying on Thursday," Luskin said.

House Democratic leaders subpoenaed Sondland on Tuesday to testify and provide documents related to the impeachment inquiry, which has largely centered on President Donald Trump's request to Ukraine's president to "look into" unsubstantiated corruption allegations against former Vice President Joe Biden and his son.

The subpoena was issued hours after Sondland was ordered by the White House not to appear for a scheduled deposition with the Democrat-led House committees leading the impeachment probe. It also came just after the White House said in a defiant letter to House leaders that it would not cooperate with the Democrats' impeachment inquiry.

House Democrats fumed about the interference in the inquiry, which Trump has described as a "witch hunt" akin to former special counsel Robert Mueller's Russia probe, which concluded earlier this year. House Intelligence Chairman Adam Schiff, D-Calif., accused the White House of "further acts of obstruction of a coequal branch of government."

"Ambassador Sondland has at all times acted with integrity and in the interests of the United States. He has no agenda apart from answering the Committees' questions fully and truthfully," Luskin said in the statement. But "federal law and State Department regulations prohibit him from producing documents concerning his official responsibilities," he said.

Sondland's text messages with other U.S. diplomats were released last week after they were given to those House panels by former U.S. special envoy to Ukraine Kurt Volker during his own deposition. In a Sept. 9 exchange, Bill Taylor, a senior U.S. diplomat in Ukraine, told Sondland: "I think it's crazy to withhold security assistance for help with a political campaign."

Sondland responded: "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 [Ukraine President Volodymyr Zelensky] promised during his campaign."

The Wall Street Journal and other outlets reported that Sondland had spoken directly with Trump in a phone call before sending his "crystal clear" rebuke to Taylor.

Click here to read those texts.

Luskin's announcement came less than two hours before another key diplomat, former U.S. ambassador to Ukraine Marie Yovanovich, was scheduled for her own deposition before the House Intelligence, Oversight and Foreign Affairs committees. The executive intervention in Sondland's deposition has raised concerns that Yovanovich might also be blocked from speaking with the investigators

Yovanovich had been ousted as the ambassador to Ukraine in the spring, following months of complaints from Trump allies including his lawyer, former New York Mayor Rudy Giuliani, that she was hindering efforts to spur Kyiv to investigate the Bidens, the Journal reported last week, citing people familiar with the matter.

Yovanovich and Sondland were both mentioned in a whistleblower complaint that accused Trump of "using the power of his office to solicit interference from a foreign country in the 2020 U.S. election."

Sondland had donated $1 million to Trump's inaugural committee. He was selected to be Trump's EU ambassador in March 2018.

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