Ex-Trump campaign adviser Rick Gates close to plea deal with Robert Mueller

WASHINGTON: US President Donald Trump's former campaign adviser Rick Gates has finalised a plea deal with special counsel Robert Mueller's office, indicating that he would cooperate in the ongoing probe over Russian interference in the 2016 presidential election.

Gates has already spoken to Mueller's team about his case and has been in plea negotiations for about a month, informed officials told CNN on Thursday. 

He has had what criminal lawyers call a "Queen for a Day" interview, in which a defendant answers any questions from the prosecutors' team, including about his own case and other potential criminal activity he witnessed.

Gates' cooperation could be another building block for Mueller in a possible case against Trump or key members of his team.

Once a plea deal is in place, Gates would become the third known cooperator in Mueller's sprawling probe, CNN reported. 

It would also increase the pressure to cooperate on Gates' co-defendant Paul Manafort, Trump's former campaign chairman, who has pleaded not guilty to Mueller's indictment and is preparing for a trial on alleged financial crimes unrelated to the campaign. 

Gates pleaded not guilty on October 30, 2017, alongside Manafort.

"Nobody (who's charged) goes in to provide incriminating information to the government unless it's part of plea negotiations," said a criminal defence attorney who represents a witness in the case. 

In a Queen for a Day interview, a defendant can typically admit to crimes with little additional consequences, unless he or she lies.

However, it was still unclear what Gates, who outlasted Manafort in the campaign and later worked on the Trump inaugural efforts, could share that would be of value to the Russian collusion investigators.