Updated at 1:38 p.m. ET
Secretary of State Mike Pompeo has publicly acknowledged that he was listening to the July 25 phone call between President Trump and Ukrainian President Volodymyr Zelenskiy that has sparked an impeachment inquiry.
"I was on the phone call," Pompeo said Wednesday in Rome.
During that call, Zelenskiy expressed appreciation for U.S. defense help and Trump responded by saying, "I would like you to do us a favor though" — and asked the Ukrainian leader to work with Attorney General Bill Barr and Trump's personal lawyer Rudy Giuliani on an investigation into the family of former Vice President Joe Biden, Trump's potential rival in the 2020 presidential election.
Pompeo discussed the call during a joint news conference alongside Italian Foreign Minister Luigi Di Maio. The secretary is on a weeklong European trip that includes stops at the Vatican as well as in Montenegro, North Macedonia and Greece.
Later Wednesday, the State Department's inspector general is expected to meet with key congressional committees dealing with the Ukraine issue. The inspector general's office sent a request for an urgent meeting Tuesday, telling lawmakers that the meeting is to discuss documents obtained from the State Department's Office of the Legal Adviser.
The bipartisan meeting, which is to be held at a secure facility, will include the Senate Foreign Relations Committee and House Foreign Affairs Committee, along with panels on homeland security, oversight and intelligence.
Hours after Pompeo spoke, House Speaker Nancy Pelosi said the U.S. system of checks and balances is under threat from the Trump administration.
"We see the actions of this president being an assault on the Constitution," she said.
Pelosi was joined at her weekly news conference on Capitol Hill by fellow California Democrat Adam Schiff, the House Intelligence Committee chairman who is leading the impeachment inquiry.
"We are deeply concerned about Secretary Pompeo's effort now to potentially interfere with witnesses ... many of whom are mentioned in the whistleblower complaint" about Trump's phone call, Schiff said.
President Trump responded to Schiff and Pelosi's words with scorn, issuing a tweet in which he called Schiff a "lowlife" and said he "should only be so lucky to have the brains, honor and strength of Secretary of State Mike Pompeo."
In a second tweet, Trump said, "The Do Nothing Democrats should be focused on building up our Country, not wasting everyone's time and energy on BULLSHIT."
Pompeo's admission comes 10 days after he deflected questions about the Ukraine call when the topic came up during an interview with Martha Raddatz on ABC News' This Week.
During the segment, Raddatz summarized news reports about the call and noted Trump's insistence that it was "a perfectly fine and respectful conversation." She asked the secretary what he knew about Trump and Zelenskiy's conversation regarding Biden — and Pompeo replied, "So, you just gave me a report about a I.C. [intelligence community] whistleblower complaint, none of which I've seen."
Pompeo went on to describe the Trump administration's policy toward Ukraine but did not disclose that he had been on the phone call. When Raddatz followed up by asking about Trump's request for an investigation, Pompeo said, "I think I saw a statement from the Ukrainian foreign minister yesterday, said there was no pressure applied in the course of the conversation."
At the time, Pompeo didn't seem to expect the White House to release an account of the call, a move he said was rare.
"It wouldn't be appropriate to do so, except in — in the most extreme circumstances," Pompeo said, adding, "There's no evidence that that would be appropriate here at this point."
The secretary confirmed his participation in the call a day after news reports that he took part. In response to those reports, key House Democrats issued a statement saying that Pompeo "is now a fact witness in the House impeachment inquiry."
Congressional Democrats and Pompeo have been trading accusations that each side is attempting to intimidate or bully witnesses in the impeachment inquiry. On Tuesday, House Democrats postponed what had been expected to be the first in a series of depositions of current and former State Department staffers after Pompeo raised objections.
As NPR's Franco Ordoñez reported, that initial deposition had been expected to take place in a closed session Wednesday between former U.S. Ambassador to Ukraine Marie Yovanovitch and the House Intelligence Committee. That session is now set for Oct. 11.
During his remarks in Rome, Pompeo reiterated his criticism of how the House impeachment inquiry is being handled — particularly Democrats' approach in seeking testimony from State Department personnel.
Pompeo said potential witnesses were contacted directly by investigators and told they could not be accompanied by State Department attorneys during testimony — which he said raises separation of powers concerns for the Trump administration.
"They contacted State Department employees directly — told them not to contact legal counsel at the State Department," Pompeo said.
Pompeo said that while the State Department will cooperate with requests from Congress as required by the Constitution, "we are going to do so in a way that is consistent with the fundamental values of the American system."
Hours later, Schiff said that if the Trump administration attempts to "stonewall" the impeachment process, such actions "will be considered further evidence of obstruction of justice, and of course, that was an article of impeachment against Nixon — the obstruction of the lawful functions of Congress, that is."
Another closed deposition is scheduled for Thursday, when lawmakers will question another former U.S. envoy to Ukraine, Kurt Volker.
Schiff said that Intelligence Community Inspector General Michael Atkinson will testify before his House committee on Friday. In that session, Schiff added, lawmakers will seek to learn more about how Atkinson corroborated the whistleblower complaint and what led him to find it "both credible and urgent."
NPR's Michele Kelemen contributed to this report.