Secretary of State Mike Pompeo was listening in on the controversial July call between President Donald Trump and Ukrainian President Volodymyr Zelenskiy, multiple sources familiar with the matter told ABC News.
During the call, which took place on July 25, Trump repeatedly pressed Ukraine's president to work with his personal attorney, Rudy Giuliani, and Attorney General William Barr to investigate former Vice President Joe Biden and his son, Hunter.
The call generated a complaint from an anonymous whistleblower, who believed the president abused his office calling for the investigation into his political rival. News of the complaint, and the White House's release of a summary of the call, has prompted an impeachment inquiry.
The Wall Street Journal first reported the news.
The State Department has not responded to a request for comment on whether Pompeo was on the call.
Pompeo did not respond to general questions about Ukraine or Giuliani during a photo opportunity with Indian Foreign Minister Subrahmanyam Jaishankar Monday afternoon.
He appeared on "This Week" on Sept. 22, when he made no mention of being on the call with Ukraine's president when asked about it. He said he had not seen the whistleblower's complaint.
"I think I saw a statement from the Ukrainian foreign minister yesterday, said there was no pressure applied in the course of the conversation," Pompeo told Martha Raddatz at the time. "I do think if Vice President Biden behaved inappropriately, if he was protecting his son and intervened with the Ukrainian leadership in a way that was corrupt, I do think we need to get to the bottom of that."
The secretary of state left Monday evening for a week-long trip to Europe, including stops in Italy, Montenegro, Macedonia and Greece.
Pompeo has also not said whether the department will comply with House Democrats' subpoena over information related to the call by the Friday deadline, or whether its five senior officials will show up for their depositions.
ABC News' Conor Finnegan contributed to this report.