Donald Trump's former chief of staff said Tuesday he was no longer willing to cooperate with the probe into January's assault on the US Capitol, prompting investigators to threaten him with criminal prosecution.
Mark Meadows, who failed to appear before the congressional panel last month, is seen as a key witness to Trump's role in efforts to overturn the election by undemocratic means.
Having initially snubbed a subpoena to testify before the House of Representatives committee, Meadows later reached an agreement on sharing information with lawmakers -- before reversing course again.
"Now actions by the select committee have made such an appearance untenable," Meadows' attorney, George Terwilliger, said in a new letter to the committee circulated among US media.
The lawyer said Meadows' change of mind had come after he learned over the weekend that the committee had "issued wide ranging subpoenas for information from a third party communications provider."
"We now have every indication from the information supplied to us last Friday -- upon which Mr. Meadows could expect to be questioned -- that the select committee has no intention of respecting boundaries concerning executive privilege," added Terwilliger.
Meadows was serving as Trump's chief of staff when backers of the former president stormed the US Capitol on January 6 in a bid to halt the certification of Democrat Joe Biden's presidential election victory.
Trump has invoked "executive privilege" -- a carve-out available in theory only to sitting presidents to protect sensitive private exchanges with aides -- in a bid to avoid having to turn over documents requested by the committee.
The panel rejected Meadows' executive privilege claim, noting that the hardline former Republican congressman had provided much detail about the attack, including his conversations with then-president Trump, in a new book.
In an interview aired late Tuesday on conservative broadcaster Fox News, Meadow said that "hopefully the courts can work it out," adding that he had tried to be accommodating with non-privileged information "while making sure that executive privilege is protected."
Panel chairman Bennie Thompson and his deputy Liz Cheney said in a statement they planned to go ahead with a deposition of the Trump loyalist scheduled for Wednesday.
"If indeed Mr. Meadows refuses to appear, the select committee will be left no choice but to advance contempt proceedings and recommend that the body in which Mr. Meadows once served refer him for criminal prosecution."
'Fight like hell'
House investigators believe Meadows, former White House strategist Steve Bannon and other Trump advisors and staffers could have information on links between the White House and the mob of Trump supporters that stormed the Capitol.
Bannon was arrested last month on a contempt of Congress charge after refusing his own subpoena and a federal judge sitting for a preliminary hearing Tuesday set July 18 for his trial.
The committee has subpoenaed a number of Trump's allies, as it closes in on the actions of those involved in planning the rallies in Washington that preceded the assault on Congress.
Trump urged his supporters to march on the Capitol and "fight like hell" in a fiery speech on January 6 that was the culmination of months of baseless fraud claims about a contest he had lost fairly to Biden.
News of the about-face by Meadows came as the watchdog overseeing the US Capitol Police told Congress the agency had not done enough since the assault to guarantee lawmakers' safety in the event of another attack.
Inspector General Michael Bolton told the Senate Rules Committee that of 200 security upgrades the Capitol Police provided to the inspector general, only 61 had been made.
He said the agency "lacks the overall training infrastructure to meet the needs of the department, the level of intelligence gathering and expertise needed, and an overall cultural change needed."
"The United States Capitol Police agrees with the inspector general that the department must continue to improve and expand its intelligence and protective capabilities," the force said in a statement responding to Bolton.