US Secretary of State Mike Pompeo has confirmed he was listening in as the US President asked Ukraine to investigate a political opponent.
The call - between Donald Trump and President Volodymyr Zelensky - is at the centre of a Democratic impeachment inquiry against Donald Trump.
Mr Pompeo dodged questions about the call in an interview just days ago.
President Trump denies improperly pressuring Ukraine and has accused opponents of mounting a "coup".
During the conversation, which triggered a whistleblower's formal complaint, the US president asked Mr Zelensky to investigate Democratic rival Joe Biden and his son Hunter.
Mr Pompeo's admission during a news conference in Italy came after media reported he was party to the conversation as well. "I was on the phone call," Mr Pompeo said.
He did not directly answer a question on whether anything in the phone call alarmed him, but said it had focused on US policy with Ukraine.
"It's been remarkably consistent, and we will continue to try to drive those set of outcomes," he said.
On Tuesday, Mr Pompeo wrote to Democrats leading the impeachment effort to remove Mr Trump from office to say that he objected to their effort to "bully" five former and current state department officials who they wish to interview.
In other developments:
- Russia's President Vladimir Putin has said he always assumes phone calls with foreign leaders could be made public. CNN reported the White House had tried to restrict access to such conversations.
- The state department's Inspector General has requested "urgent" meetings today with congressional committees to brief them on Trump White House interactions with Ukraine.
- Mr Trump's personal lawyer Rudy Giuliani told Fox News he wants to sue Democrats in the House of Representatives for "interfering" with the president's business.
- In a tweet, Mr Trump said the impeachment effort to remove him from office is a "coup, intended to take away the Power of the People".
Mr Pompeo's presence on the call was reported earlier this week, but it is the first time he has addressed it directly.
When asked in a 22 September interview with ABC News what he knew of the conversation, Mr Pompeo said he had just been given the "whistle-blower complaint, none of which I've seen".
"You just gave me a report... none of which I've seen," Secretary of State Mike Pompeo tells @martharaddatz when asked about a report that President Trump pressed the President of Ukraine to work with Rudy Giuliani to investigate Joe Biden's son. https://t.co/CaWsz4XapY pic.twitter.com/coDl6mG6Dy— ABC News (@ABC) September 22, 2019
Pressed on whether Mr Trump's reported comments were appropriate, he responded: "I think I saw a statement from the Ukrainian foreign minister yesterday, said there was no pressure applied in the course of the conversation."
Mr Pompeo - the top US diplomat - was hit last week with a House subpoena to testify. On Tuesday three Democratic committee chairmen accused him of "stonewalling" the impeachment inquiry, adding that he is a "fact witness" to the probe.
His three day trip to Italy, which includes a private audience with Pope Francis, has largely been overshadowed by the impeachment efforts in Washington.
Quick facts on impeachment
- Impeachment is the first part - the charges - of a two-stage political process by which Congress can remove a president from office.
- If the House of Representatives votes to pass articles of impeachment, the Senate is forced to hold a trial.
- A Senate vote requires a two-thirds majority to convict - unlikely in this case, given that Mr Trump's party controls the chamber.
- Only two US presidents in history - Bill Clinton and Andrew Johnson - have been impeached but neither was convicted and removed.
- President Nixon resigned before he could be impeached.