Lawmakers probing the deadly January 6 assault on the US Capitol issued subpoenas Monday to top aides of Donald Trump who are accused of plotting to overturn his defeat in a "war room" at a luxury Washington hotel.

Lawyer John Eastman was among a number of advisors summoned to explain their role in the talks at the Willard InterContinental in the days surrounding the attack, when Trump supporters stormed Congress to halt certification of Democrat Joe Biden's presidential election victory.

Eastman is said to have drafted a memo advising Trump that his vice president Mike Pence had the authority to simply reject the results in certain states and deny Biden the victory.

He also reportedly hosted a January 2 meeting where he told around 300 state legislators it was their duty to fix "this egregious conduct and make sure that we're not putting in the White House some guy that didn't get elected."

Crucially, Eastman reportedly participated in a January 5 "war room" meeting at the Willard and spoke at a rally near the White House that preceded the attack.

He reportedly sent Pence's lawyer an email during the siege, saying it had happened was "because YOU and your boss did not do what was necessary to allow this to be aired in a public way."

Police push back supporters of US President Donald Trump after they stormed the Capitol building on January 6, 2021
Police push back supporters of US President Donald Trump after they stormed the Capitol building on January 6, 2021 AFP / ROBERTO SCHMIDT

"Your documents and testimony are directly relevant to the select committee's investigation, as you appear to have been instrumental in advising President Trump that Vice President Pence could determine which electors were recognized on January 6, a view that many of those who attacked the Capitol apparently also shared," the committee told Eastman in its subpoena.

The other targets are largely aides or official members of Trump's reelection campaign whom the panel says were involved in promoting his lie that the presidential election was stolen.

They include former New York police chief Bernard Kerik and one-time campaign advisor Jason Miller, who are both said to have attended the January 5 "war room."

Mike Flynn, Trump's disgraced former national security advisor was also summoned alongside reelection campaign manager William Stepien and executive assistant Angela McCallum.

"The select committee needs to know every detail about their efforts to overturn the election, including who they were talking to in the White House and in Congress, what connections they had with rallies that escalated into a riot, and who paid for it all," panel chairman Bennie Thompson said in a statement.

It is the first round of subpoenas issued by the committee since the House asked the Department of Justice to pursue criminal contempt charges against Trump ally Steve Bannon for defying his congressional order to appear.