White House chief of staff denies calling Donald Trump 'an idiot'

New details have emerged on the rift between White House chief of staff John Kelly and President Donald Trump, with one former administration official saying Mr Kelly privately called Mr Trump "an idiot" last year.

Mr Kelly's insult, confirmed to the Associated Press by the former official, came as his clashes with Mr Trump over policy and personnel grew louder and more frequent.

The chief of staff, who has cast himself as safeguarding the public from the president, has also threatened to quit the White House on several occasions.

Mr Kelly's disparaging remark was first reported on Monday by NBC News.

In a statement, Mr Kelly called the report "total BS" and characterised his relationship with Mr Trump as "incredibly candid and strong".

He added of the president: "He always knows where I stand and he and I both know this story is total BS."

Mr Kelly's top aide Zachary Fuentes also disputed the characterisation, saying he had never heard Mr Kelly describe the president that way.

"Remember, he is a Marine. Once a Marine, always a Marine," said Mr Fuentes. "The office of the commander in chief is held to the highest regard."

Mr Trump appeared to react to the NBC report on Twitter, tweeting: "The Fake News is going crazy making up false stories and using only unnamed sources (who don't exist)."

He added: "The White House is running very smoothly."