Members of the Trump campaign's inner circle, including his eldest son and son-in-law, are being called before Senate committees to talk about the 2016 election.
Donald Trump Jr is set to appear before the Senate judiciary committee on Wednesday along with former campaign chairman Paul Manafort, according to a witness list released by the panel.
Also, a lawyer for Trump's powerful son-in-law and adviser said Jared Kushner would speak to the Senate intelligence committee on Monday.
"Working with and being responsive to the schedules of the committees, we have arranged Mr Kushner's interview with the Senate for July 24," Kushner's lawyer, Abbe Lowell, said in a statement on Wednesday.
"He will continue to co-operate and appreciates the opportunity to assist in putting this matter to rest."
That meeting will apparently take place behind closed doors.
The three men will almost certainly be asked about their attendance at a June 2016 meeting with a Russian lawyer.
That gathering was arranged via emails that advertised it would reveal damaging information about Hillary Clinton.
The lawyer, Natalia Veselnitskaya, also said on Wednesday she was ready to testify before the US Senate and "clarify the situation".
The meeting raised new questions about the Trump campaign's possible ties to Moscow, which are being scrutinised by federal and congressional investigators.
These questions have only intensified as the identities of other Russia-connected participants have become known.
"I am ready to clarify the situation behind the mass hysteria but only through lawyers or testifying in the Senate," Veselnitskaya said in an interview on Wednesday on Kremlin-funded RT television.
"If the Senate wishes to hear the real story, I will be happy to speak up and share everything I wanted to tell Mr Trump," she said.
That appeared to be a reference to Veselnitskaya's previous statement the meeting with Trump Jr focused on US-Russian adoption policies and a US sanctions law.
Veselnitskaya has denied working for the Russian government.
The top Democrat on the Senate intelligence panel, Mark Warner, said on Wednesday the panel had not yet invited Veselnitskaya to testify but he wanted to hear from her and others who attended.
The Russia issue has overshadowed Trump's tenure and irritated the president, who told the New York Times on Wednesday he would not have appointed ally and former senator Jeff Sessions as attorney-general if he had known Sessions would recuse himself from oversight of the Russia probe.
"Sessions should have never recused himself and if he was going to recuse himself, he should have told me before he took the job and I would have picked somebody else," Trump said.
Share
