Former FBI Director James Comey says the Russia investigation appears to be nearing its end.

On Wednesday, he speculated that the Trump campaign chairman Paul Manafort's recent guilty pleas and agreement to cooperate with the special counsel Robert Mueller suggested Mueller was closing in on President Donald Trump.

"The way you normally do investigations is you work from the bottom up, and so they're getting pretty high," he said.



Comey also said the investigation had been conducted in secret and he couldn't be sure of its progress.

James Comey says Robert Mueller may be nearing the end of the Russia investigation.

The former FBI director gave an interview to St. Louis Public Radio on Wednesday in which he gave an assessment of the progress made by Mueller, his predecessor at the FBI who is now serving as special counsel leading the investigation into Russian election meddling and the Trump campaign.

Comey said the fact that Paul Manafort, the former Trump campaign chairman, pleaded guilty to conspiracy and agreed to cooperate with Mueller suggested that Mueller might almost be done.

Mueller was named special counsel to lead the Russia investigation in May 2017. Chip Somodevilla/Getty Images

Comey said on Wednesday:

"I think there's an argument to be made that the conviction — the plea and cooperation by Paul Manafort — may represent that we're in the fourth quarter.

"Because the way you normally do investigations is you work from the bottom up, and so they're getting pretty high."

He added, however, that he couldn't "say with certainty" where Mueller's progress was at because the investigation had largely been conducted under wraps.

"The reason I'm hesitant to even say that is Bob Mueller's conducted his investigation like a pro," Comey said. "You know nothing about it except through his public filings, and that's the way it's supposed to be. So I can't say with certainty where he is."

Listen to Comey discuss this around the 8:00 mark in the clip below:

Mueller took charge of the investigation 16 months ago, in May 2017, shortly after President Donald Trump fired Comey as FBI director.

Manafort last week pleaded guilty to one count of conspiracy to obstruct justice and one count of conspiracy against the US in a case that centered on his political consulting work from 2006 to 2015 for pro-Russian interests.

The White House press secretary, Sarah Huckabee Sanders, has said Manafort's case "had absolutely nothing to do with the president or his victorious 2016 presidential campaign."

The former Trump attorney Michael Cohen and the former Trump campaign chairman Paul Manafort. Both have pleaded guilty to federal crimes and agreed to cooperate in investigations into the US president. Associated Press/Craig Ruttle; Associated Press/Alex Brandon; Business Insider

'The perfect storm of cooperators'

Trump's longtime personal lawyer Michael Cohen is also cooperating with an investigation by the Manhattan US attorney's office into his and Trump's dealings leading up to the election.

He pleaded guilty last month to five counts of tax evasion, one count of bank fraud, and two counts related to campaign-finance violations.

Allen Weisselberg, the Trump Organization's longtime chief financial officer, was granted immunity by federal prosecutors last month so he could share information about Cohen and Trump.

One former federal prosecutor said federal investigators had "the perfect storm of cooperators."