A man who said he wanted to "assassinate" Donald Trump has been arrested outside the White House, police have said.

Roger Hedgpeth, 25, was taken into custody on Saturday afternoon after telling a Secret Service agent that he was there to kill the president.

He told the agent: "I have a knife to do it with."

Police found a three-and-a-half inch blade in a sheath on his left hip and an empty gun holster on his right hip, according to a Metropolitan Police Department report seen by the Associated Press.

Mr Hedgpeth was then arrested and taken for a mental health assessment at a local hospital.

His vehicle was impounded. It was not immediately clear where he was from or whether he had a lawyer to comment on his behalf.