Former Director of National Intelligence James Clapper said Wednesday that he's far from sure that special counsel Robert Mueller's investigation will clear up questions about President Trump and Russia.

He said he was hopeful the Mueller probe will provide some answers, but warned it might not even draw a conclusion on whether there was collusion between the Trump campaign and Moscow.

"I think the hope is that the Mueller investigation will clear the air on this issue once and for all. I'm really not sure it will, and the investigation, when completed, could turn out to be quite anti-climactic and not draw a conclusion about that," Clapper said Wednesday on CNN.

Clapper, a frequent critic of Trump's, said people in the intelligence community see a strange deference on the president's part toward Russian President Vladimir Putin.

"The strange thing I think that has bothered a lot of people both in and out of the intelligence community is this strange personal deference to Putin by the president. I've speculated in the past that the way Putin behaves is to treat President Trump as an asset," Clapper said Wednesday.

He added that if Trump were indeed advancing Putin's interests, he would more likely be doing so unwittingly.

The White House has lashed out at Clapper over his criticism in the past and announced in August it was reviewing existing security clearances for Clapper and several other former intelligence and law enforcement officials who have criticized the White House.

Speculation has ramped up over Trump's relationship with Russia after it was reported last month that the Justice Department had opened an investigation into whether the president was working on behalf of Moscow's interests.

Former acting FBI Director Andrew McCabe on Friday claimed that he believes "it's possible" Trump is a Russian asset.

McCabe, who was fired from the FBI by then-Attorney General Jeff Sessions shortly before his retirement, has frequently criticized the president since his dismissal.

- This post was updated at 6:52 p.m. to clarify the circumstances surrounding McCabe's firing.