Donald Trump's daughter Ivanka will testify Tuesday before the probe into the 2021 Capitol assault, US media reported, as lawmakers ramp up attempts to seek evidence from the inner circle of the former president.

The House January 6 select committee had asked the 40-year-old businesswoman -- a senior advisor to her father -- to appear voluntarily, telling her it had evidence that she had pleaded with him to call off the violence as his supporters stormed Congress.

"Testimony obtained by the committee indicates that members of the White House staff requested your assistance on multiple occasions to intervene in an attempt to persuade President Trump to address the ongoing lawlessness," chairman Bennie Thompson wrote to her in January.

Investigators are looking into how the attack, which shut down Congress as lawmakers were certifying the 2020 presidential election, took place and to what extent then-president Trump and his aides had a part in encouraging it.

The committee has already spoken to around 800 witnesses -- including Ivanka Trump's husband Jared Kushner -- and has been working its way through 90,000 documents and more than 435 phone tip-offs.

The committee didn't immediately respond to a request for comment on the former first daughter's appearance, first reported by NBC, ABC and Politico.

She appears to have direct knowledge of her father's attempt to persuade then-vice president Mike Pence to stop the counting of electoral votes, the committee said when it asked her to come forward.

"As January 6 approached, President Trump attempted on multiple occasions to persuade vice president Pence to participate in his plan," Thompson wrote.

"One of the president's discussions with the vice president occurred by phone on the morning of January 6. You were present in the Oval Office and observed at least one side of that telephone conversation."

Burner phones 

The eldest of the former president's two daughters, who served as director of the White House Office of Economic Initiatives and Entrepreneurship, wasn't immediately available for comment.

The White House said last week it would reject any assertion of "executive privilege" -- which allows presidents to keep certain work-related conversations with aides private -- from Ivanka Trump.  

It was not immediately clear if she would testify in-person but Kushner, also a top former White House aide, answered questions for six hours via video link last week.

The couple's cooperation comes during an intense period of revelations from the committee, which is approaching the end of its investigative phase ahead of public hearings planned for May.  

It was revealed last month that right-wing activist Ginni Thomas, wife of Supreme Court Justice Clarence Thomas, sent more than 20 texts pushing wild conspiracy theories and urging then-White House chief of staff Mark Meadows to help overturn the 2020 election.

It also emerged that White House logs given to investigators from the day of the insurrection show a gap of nearly eight hours in the record of Trump's calls, including the period covering the violence.

The committee is investigating whether it has the full record and if Trump communicated that day through phones of aides or personal disposable "burner" phones.

A federal judge last week that Trump "more likely than not" engaged in criminal conduct with his efforts to overturn the results of the election.