Kiyoshi Tanno/iStock(WASHINGTON) — A key witness in the Democratic impeachment probe, Ambassador Gordon Sondland, was barred from testifying at the last-minute Tuesday by the State Department, sources confirmed to ABC News.

Sondland worked with other senior State Department officials to facilitate conversations between President Donald Trump’s personal lawyer Rudy Giuliani and top Ukrainian officials as the president and Giuliani sought a Ukrainian investigation into Trump’s political opponents.

In a series of text messages revealed last week, Sondland is seen consulting with former U.S. special envoy for Ukraine Kurt Volker to press Ukraine’s new president Volodymyr Zelenskiy and his top aides to investigate, in order to obtain a meeting at the White House and later military aid. In those texts, Sondland denied that there were any “quid pro quo’s.”

Sondland was scheduled to appear before staff from three House committees investigating Trump’s actions around Ukraine and his controversial July 25 call with Zelenskiy. But early Tuesday morning, he was told not to appear, according to his lawyer Robert Luskin.

“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,” Luskin said in a statement to ABC News.

“Ambassador Sondland is profoundly disappointed that he will not be able to testify today,” Luskin added. “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.”

“Ambassador Sondland hopes that the issues raised by the State Department that preclude his testimony will be resolved promptly. He stands ready to testify on short notice, whenever he is permitted to appear,” Luskin said.

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