The pro-Trump Breitbart News site, back under the leadership of former senior White House chief strategist Steve Bannon, is prepared to campaign for the president's impeachment if he strays from his campaign promises, according to a new report.

An article published Sunday night in Vanity Fair quoted an anonymous Breitbart staffer as saying that the website is willing to side with House Speaker Paul Ryan, a frequent target of Breitbart, if Trump shows signs of veering from his nationalist agenda.

"We're prepared to help Paul Ryan rally votes for impeachment," the source said.

A source at Breitbart told the Washington Examiner on Monday that Bannon's return to the site has emboldened the staff in terms of its coverage on the administration.

Bannon resigned from his White House position last week and said in a media interview that, "The Trump presidency that we fought for and won, is over."

Breitbart has remained supportive of Trump but has occasionally criticized some of his staffing choices, especially national security adviser H.R. McMaster.