U.S. Ambassador to the European Union Gordon Sondland will testify before three House impeachment committees next week, complying with a subpoena from Democrats as part of their impeachment inquiry despite the State Department's orders not to appear.

In a Friday statement from Sondland's lawyer, the EU ambassador agreed to appear for a scheduled deposition Thursday but said he won't provide requested documents related to the Ukraine scandal, citing federal law and State Department regulations that "prohibit him from producing documents concerning his official responsibilities."

"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," Sondland's lawyer said in a statement provided to Politico. "Ambassador Sondland has at all times acted with integrity and in the interests of the United States. He has no agenda from answering the committee's questions fully and truthfully."

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Sondland was scheduled to appear on Tuesday before the House Intelligence Committee, the House Foreign Affairs Committee and the House Oversight and Reform Committee as part of Democrats' inquiry investigating Trump's request that Ukranian President Volodymyr Zelenskiy look into former Vice President Joe Biden and his son Hunter Biden.

But the State Department directed him at the last minute not to testify. Following his decision not to appear, House Democrats subpoenaed Sondland to appear for a closed-door deposition.

Sondland has emerged as a key witness in the Democrats' impeachment inquiry into Trump's July 25 call with Zelenskiy and an intelligence community whistleblower complaint about the two leaders' communication. House Democrats are also investigating Trump's decision to freeze military aid to Ukraine.

In text messages between Trump officials that were recently released to Congress, Sondland discussed the decision to withhold funding from Ukraine with top Ukranian embassy official Bill Taylor last month. Taylor voiced skepticism, saying in a Sept. 9 message, "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 President Zelensky promised during his campaign. I suggest we stop the back and forth by text."