Congressional investigators plan to question the former chairman of the Trump campaign and will subpoena him if necessary, the Senate Judiciary Committee panel's chairman has said.
Republican Senator Chuck Grassley said he and the committee's top Democrat, Dianne Feinstein have agreed to try to bring Paul Manafort before the panel for questioning about the government's enforcement of a law requiring registration of foreign lobbyists.
Ms Feinstein's office confirmed that they plan to question him.
Mr Manafort would certainly also be asked about his participation in a Trump Tower meeting last June with President Donald Trump's eldest son and son-in-law, where the purpose was to hear potentially damaging information about Hillary Clinton from a Russian lawyer.
Mr Manafort disclosed the meeting in a package of information he provided to the Senate and House intelligence committees, who have been investigating potential coordination between Russia and the Trump campaign, as is Robert Mueller, the former FBI director appointed by the Justice Department as the special counsel.
"Obviously it would be appropriate for anybody to get into anything that went on at that meeting, and he was at that meeting," Mr Grassley told Iowa reporters.
A person close to Mr Manafort said that he has not yet received a letter from the committee about a possible interview.
Separately, Representative Adam Schiff, the top Democrat on the House intelligence committee, said his panel wants to look at the use of Russian social media "trolls" and whether they were connected to the Trump election campaign.
That concern is "certainly something we want to explore," along with the Trump campaign's data analytics, Mr Schiff said.
Mr Trump's son-in-law, Jared Kushner, oversaw digital strategy for the campaign.
"One of the biggest crimes we're looking at is the hacking of data, so understanding how it was used certainly needs to be part of the investigation," said Representative Eric Swalwell, another Democratic member of the committee.
"We want to understand what data was hacked, where it was stored and if it was weaponised at all, whether it was by Russia or the campaign."
The politicians spoke one day after Donald Trump Jr disclosed on Twitter a series of emails that revealed his eagerness to hear negative material on Clinton from a Russian lawyer.
The exchange showed Mr Trump Jr conversing with a music publicist who wanted him to meet with a "Russian government attorney" who supposedly had dirt on Clinton as "part of Russia and its government's support for Mr Trump".
He was told the Russian government had information that could "incriminate" Mrs Clinton and her dealings with Russia.
"If it's what you say I love it especially later in the summer," Mr Trump Jr said in one email response.
In an interview before departing for France, Mr Trump told Reuters that he did not know about the meeting "until a couple of days ago when I heard about this". He also said that he did not fault his son for attending. "I think many people would have held that meeting," he said.