The US House intelligence panel will interview two of US president Donald Trump's associates behind closed doors this week as congressional committees step up their investigations into Russian meddling in the 2016 election.
Trump associate Roger Stone and former staffer Boris Epshteyn are scheduled to talk to the House panel this week.
Mr Stone confirmed his interview will be held on Tuesday. Mr Epshteyn will also speak to the committee this week, according to a source.
The interviews come as the House and Senate intelligence panels examine meddling and scrutinise the spread of false news stories and propaganda on social media.
The Senate intelligence committee will speak to officials from Twitter on Wednesday, also behind closed doors.
Mr Stone is a Republican strategist who has known Mr Trump for many years and informally advised him during the 2016 campaign.
He has said he communicated during the presidential campaign with Guccifer 2.0, the unnamed hacker who has taken credit for breaking into Democratic National Committee email servers.
But Mr Stone has denied that he worked with Russian officials to influence the presidential election.
Mr Stone has been outspoken in his own defence and asked for his appearance to be public. But he said the House panel insisted on holding the session behind closed doors.
California representative Adam Schiff, the top Democrat on the House Intelligence Committee, suggested in March that Mr Stone had a direct line to Russian hackers based on his comments predicting the release of former Hillary Clinton campaign chairman John Podesta's emails.
Mr Stone said then that Mr Schiff had "slimed me in public, and I'd like to have an opportunity to defend myself in public".
Last week, Mr Stone continued his criticism of the California Democrat, saying the committee is "full of Schiff".
Mr Epshteyn, who grew up in Moscow, worked a short time in the White House press office. He left in March and now works as a political analyst for right-leaning Sinclair Broadcasting.
Beyond this week, the committees plan for a busy October, with the Senate intelligence panel bringing Mr Trump's personal lawyer, Michael Cohen, in for a public hearing on October 25.
Senate committee leaders have also said they want Facebook and other social media outlets to appear publicly next month.
Attorney General Jeff Sessions will testify on October 18 before the Senate Judiciary Committee - the first time since he was confirmed in February.
Mr Sessions has recused himself from Russia investigations, and the Justice Department has appointed special counsel Robert Mueller to investigate the involvement of Russia in the US election.
But Mr Sessions is still likely to face questions about Russia and the firing of former FBI director James Comey.
Mr Sessions also has been subpoenaed by House Intelligence chairman Devin Nunes, who is asking the Justice Department and the FBI for documents related to a dossier of salacious allegations involving President Trump and possible ties to Russia.
If the documents are not produced, the committee is seeking to compel Mr Sessions and FBI director Christopher Wray to testify in an open hearing.