Paul Manafort volunteers to testify in Russia probe as committee cancels other testimony Manafort was not a subject of the "incidentally collected" information.

 -- House Intelligence Committee Chairman Devin Nunes, R-Calif., announced Friday that Paul Manafort, former chairman of Donald Trump's presidential campaign, has volunteered to testify in front of the committee.

Nunes told the press in his announcement Friday that it is up to Manafort to decide whether or not his testimony will be in an open hearing. A Senate source tells ABC News that the Senate Intelligence Committee will also meet with Manafort as part of its similar investigation.

A spokesman for the former Trump campaign chairman told ABC News that Manafort contacted the House committee to volunteer his testimony for the panel's investigation of Russian interference in the presidential election and of whether any Trump associates colluded in those actions.

"As Mr. Manafort has always maintained, he looks forward to meeting with those conducting serious investigations of these issues to discuss the facts," the spokesperson said.

Nunes also clarified that Manafort is not one of the individuals caught up in incidental surveillance of the Trump transition team. Earlier this week Nunes drew skepticism when he revealed to the press and the White House that he had new information from secret sources suggesting the Obama administration had collected surveillance on members of the Trump transition team and possibly Trump himself in the course of the investigation of Russia.

The committee chairmasaid today that the House Intelligence Committee has not received documents from the National Security Administration to officially corroborate those claims from his secret sources and said he doesn't expect to get them today.

Democrats have asserted that no matter what NSA documents the committee receives, the president's claims that his predecessor wiretapped him during the campaign will never be vindicated. Many have called into question Nunes' ability to conduct a fair investigation of the Russia matter.

Nunes also announced today that the committee has called on FBI Director James Comey and the National Security Agency director, Adm. Mike Rogers, to return to the Hill to brief the House Intelligence Committee in a closed session. Nunes said the panel needs a private session with Comey and Rogers because there are things they couldn’t talk about publicly in Monday's public hearing.

In anticipation of that closed meeting, a previously planned March 28 hearing is now postponed, Nunes also announced.

A number of senior former intelligence and Justice Department officials had been invited to the March 28 hearing, including former CIA Director John Brennan, former Director of National Intelligence James Clapper, and former Acting Attorney General Sally Yates.

The ranking Democratic member on the Intelligence Committee, Adam Schiff, D-Calif., tweeted that Chairman Nunes cancelled the hearing in an "attempt to choke off public info."