Trump looking forward to Russia probe

As to when it might happen, Mr Trump said: "Yesterday they were talking about two to three weeks."

Asked if he thought Mr Mueller would be fair, the president replied: "We are going to find out... I hope so."

What else did Trump tell the press?

Mr Trump told reporters that his former rival Hillary Clinton was not prepared to be interviewed under oath by the FBI about her use of a private email server.

The Republican president also said he did not recall asking an acting FBI director about his voting record.

"I don't think I did," he said. "I don't know what's the big deal with that."

Andrew McCabe, who took over the FBI after the president fired its previous director, James Comey, last May, said he found Mr Trump's Oval Office question "disturbing".

Mr McCabe said he told the president that he did not vote in the 2016 presidential election, according to the Washington Post.

Mr Mueller is thought to be investigating whether Mr Comey's firing was an attempt to obstruct justice.

What's happened in the inquiry lately?

US Attorney General Jeff Sessions was interviewed by the Mueller inquiry for several hours last week.

The country's top prosecutor is thought to be the first member of the Trump cabinet to be questioned.

Four people have already been criminally charged as part of Mr Mueller's investigation.

Michael Flynn, the president's former national security adviser, pleaded guilty to lying to the FBI about a meeting with a Russian ambassador. Former Trump campaign manager Paul Manafort has been charged on 12 counts, including conspiring to defraud the US in his dealings with Ukraine, and conspiracy to launder money.

Mr Manafort's business associate Rick Gates was also charged with conspiracy to launder money.

A third adviser to the campaign - George Papadopoulos - pleaded guilty to lying to the FBI.