Former White House counsel Pat Cipollone made apparent desperate and last-ditch efforts to prevent then-president Donald Trump appearing before his supporters during the US Capitol riots.
A congressional committee interviewed Mr Cipollone after he was subpoenaed last week with a deadline to give sworn testimony.
Mr Cipollone has been a sought-after witness since bombshell testimony from former White House aide, Cassidy Hutchinson, revealed his attempts to stop Mr Trump from appearing in front of the violent mob.
Ms Hutchinson said Mr Cipollone urged her to persuade her boss, chief-of-staff Mark Meadows, not to let Mr Trump go to the Capitol.
The panel was told he warned Mr Trump that he would be charged with "every crime imaginable" if he did so.
The committee was also told Mr Cipollone was part of a key meeting on the Sunday before the January 6 attack when Justice Department officials at the White House threatened to resign if Trump went ahead with plans to install a new acting attorney-general who would pursue his false claims of voter fraud.
Mr Cipollone, once a staunch presidential confidant who had defended Trump during his first impeachment trial, had been reluctant to appear formally for an on-record interview.
It remains unclear exactly what evidence Mr Cipollone gave during the latest hearing.
"Any concerns Mr Cipollone has about the institutional prerogatives of the office he previously held are clearly outweighed by the need for his testimony," the committee said.
Earlier this week, Mr Trump responded to news of Mr Cipollone's cooperation on his social media platform, Truth Social, calling it bad for the country.
"Why would a future President of the United States want to have candid and important conversations with his White House Counsel if he thought there was even a small chance that this person, essentially acting as a 'lawyer' for the Country, may someday be brought before a partisan and openly hostile Committee in Congress," Mr Trump wrote.
AP/ABC
