Washington — The U.S. ambassador to the European Union told House lawmakers that he and other diplomats worked with Rudy Giuliani to pressure Ukraine to announce investigations in exchange for a White House meeting "at the express direction of the president of the United States," a "quid pro quo" scheme he says was known at the highest levels of the government.

Gordon Sondland, the ambassador, is testifying before the House Intelligence Committee on Wednesday, the fourth day of public hearings.

In his opening statement, Sondland said Secretary of State Mike Pompeo was aware of efforts to get the Ukrainian government to announce anti-corruption investigations in exchange for a coveted White House meeting. The investigations targeted supposed Ukrainian interference in the 2016 campaign and a Ukrainian gas company that had employed Hunter Biden, former Vice President Joe Biden's son.

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"The suggestion that we were engaged in some irregular or rogue diplomacy is absolutely false," Sondland said, adding that he has located emails that "show that the leadership of State, [National Security Council] and the White House were all informed about the Ukraine efforts" beginning as early as May.

"I know that members of this Committee have frequently framed these complicated issues in the form of a simple question: Was there a 'quid pro quo?' As I testified previously, with regard to the requested White House call and White House meeting, the answer is yes," Sondland said.

Read Sondland's opening statement here

Sondland said he informed Pompeo that he had spoken to Ukrainian President Volodymyr Zelensky before the July 25 call between Mr. Trump and Zelensky, relaying that he had told Zelensky he should mention he "intends to run a fully transparent investigation and will 'turn over every stone.'"

"Everyone was in the loop. It was no secret. Everyone was informed via email on July 19, days before the presidential call," Sondland said.

Weijia Jiang contributed reporting.