Donald Trump's former lawyer Michael Cohen was fully co-operative during closed-door testimony before a congressional committee investigating Russia's interference in the 2016 US election, the panel's chairman says.
House Intelligence Committee Chairman Adam Schiff, a Democrat, said Cohen would return on March 6 to allow another chance to follow up on allegations of wrongdoing Cohen levelled at his former boss this week.
"I think we all feel it was a very productive interview today where he was able to shed light on a lot of issues very important to our investigation. We were able to drill down in great detail," Schiff told reporters on Thursday.
Schiff said the panel will also talk to Felix Sater, a Russian-born property developer and former business associate of Trump, in a public session on March 14 about efforts to build a Trump tower in Moscow.
Sater, who worked with Cohen on the project while Trump was running for president, has said he and Cohen at one point talked about giving a $US50 million ($A70 million) penthouse to Russian President Vladimir Putin as a way to justify raising the prices of other units in the envisioned tower.
Cohen pleaded guilty last year to lying to Congress about the Moscow project but Schiff said he answered all of the panel's questions. The testimony will eventually be made public, he said.
Cohen has spoken before three congressional panels examining Russian election meddling and any collusion with the Trump campaign.
In dramatic public testimony on Wednesday before the House Oversight Committee, Trump's one-time "fixer" accused the president of breaking the law while in office and said for the first time Trump knew in advance about a WikiLeaks dump of stolen emails that hurt his 2016 election opponent Hillary Clinton.
Committee chairman Elijah Cummings, a Democrat, said his panel would further investigate issues raised by Cohen's testimony and may try to get the president's son, Donald Trump Jr, and his former accountant, Allen Weisselberg, to testify.
Other Democrats say they will try to verify whether Trump manipulated financial statements to reduce taxes and secure bank loans, as Cohen alleged.
Democratic Representative Jim Himes said Thursday's closed-door format allowed them to explore in depth some of the issues Cohen raised on Wednesday, as well as other subjects.
Cohen is to begin a three-year prison sentence for lying to Congress about the Moscow tower project, along with other charges.
He submitted a statement in 2017 saying efforts to build the tower had ceased by January 2016, when those talks in fact continued until June of that year, after Trump had clinched the Republican presidential nomination.
