Former informal Trump adviser Roger Stone Roger Jason StoneOur Constitution is under attack by Attorney General William Barr Justice IG investigating Stone sentencing: report Romney says Trump's protest tweets 'clearly intended to further inflame racial tensions' MORE said Friday that he thinks it would be a mistake for President Trump Donald John TrumpBubba Wallace to be driver of Michael Jordan, Denny Hamlin NASCAR team Graham: GOP will confirm Trump's Supreme Court nominee before the election Southwest Airlines, unions call for six-month extension of government aid MORE to sit down for an interview with special counsel Robert Mueller Robert (Bob) MuellerCNN's Toobin warns McCabe is in 'perilous condition' with emboldened Trump CNN anchor rips Trump over Stone while evoking Clinton-Lynch tarmac meeting The Hill's 12:30 Report: New Hampshire fallout MORE.

During a CNN interview, Stone warned of a potential "perjury trap" for the president, saying Mueller could probe "some process-related crime that doesn't relate to Russia."

ADVERTISEMENT

"I obviously believe the special counsel has a political bias, as demonstrated by the FBI text messages and emails that have surfaced and the political nature of this investigation, so I think it is very dangerous for the president to do so," Stone said.

His advice to Trump came just hours after a CNN report that Trump was in the preliminary stages of preparing for a possible interview with Mueller later this year.

The president has not formally agreed to sit down with the special counsel, but has said in the past that he "would like to." His former attorney, John Dowd, resigned last month after advising Trump against such a move.

Nineteen people, including several former members of the Trump campaign, have so far been hit with criminal charges stemming from the special counsel investigation into Russia's interference in the 2016 election, including possible collusion.

Trump's former campaign chairman, Paul Manafort Paul John ManafortOur Constitution is under attack by Attorney General William Barr Bannon trial date set in alleged border wall scam Conspicuous by their absence from the Republican Convention MORE, is battling charges of money laundering and tax fraud while former campaign advisers Michael Flynn and George PapadopoulosGeorge Demetrios PapadopoulosTale of two FBI cases: Clinton got warned, Trump got investigated Trump says he would consider pardons for those implicated in Mueller investigation New FBI document confirms the Trump campaign was investigated without justification MORE have both pleaded guilty to lying to investigators.

The Washington Post reported earlier this month that Mueller told Trump's lawyers in March that the president is not a criminal target of the Russia probe, but emphasized that he is still a subject of the investigation.