Robert Mueller examining blocked Trump letter that explains his reasons for firing Comey

Robert Mueller is said to be examining the draft of a letter written by Donald Trump in which he laid out his rationale for firing FBI Director James Comey - a document that could prove crucial as the special counsel probes whether the President behaved in a way that obstructed justice.

Mr Comey was fired by Mr Trump on May 9 as the President became increasingly frustrated over the course of the FBI investigation into possible collusion between the Trump campaign and Russia’s alleged interference in the 2016 election.

At the time, he had a letter delivered to Mr Comey explaining the decision, which was written by deputy attorney general, Rod Rosenstein. It focused on Mr Comey’s handling of Hillary Clinton’s use of a private email server.

Yet reports suggest the earlier letter could provide clues to Mr Mueller as to Mr Trump’s true intention for getting rid of his FBI Director. At the time, he told a television interviewer that Mr Comey was a “grandstander” and admitted he felt the Russia probe was a distraction.

The New York Times said Mr Trump was talked out of sending the earlier letter to Mr Comey, written with the help of White House aide Stephen Miller, on the recommendation of White House lawyer Don McGahn.

The newspaper, which said it had not seen the actual letter, reported that Mr McGahn “believed that some of its contents were problematic”, which partly lead to its redrafting, effectively blocking it from being released to the public.

The earlier letter was handed over to Mr Mueller’ team by the the US Justice Department. A statement from the department said it had been fully cooperative with Mr Mueller’s investigation.

In testimony on Capital Hill in June, Mr Comey said he did not know for certain why he was fired.

But he told the Senate Intelligence Committee: “Again, I take the president’s words. I know I was fired because of something about the way I was conducting the Russia investigation was in some way putting pressure on him, in some way irritating him, and he decided to fire me because of that.”

The Associated Press said Mr Trump had been fuming about Mr Comey for weeks, and was angry that the FBI Director would not say publicly that the President was not personally under investigation. Mr Comey later confirmed that when he appeared before senators.

Mr Mueller’s office has declined to comment on the draft letter. Mr Trump’s lawyers have also refused to discuss the issue.

Ty Cobb, a White House lawyer, told the Times: “To the extent the special prosecutor is interested in these matters, we will be fully transparent with him.”