Ryan Routh charged with attempted assassination of Trump

US prosecutors have charged a man arrested near Donald Trump's Florida golf course with the attempted assassination of a presidential candidate.

It comes a day after a court filing showed Ryan Wesley Routh had written a note months ago saying he intended to kill Trump.

Routh, 58, already faces up to 20 years behind bars on two gun-related charges.

But he faces a maximum sentence of life in prison if convicted on the new, more serious charge.

“Violence targeting public officials endangers everything our country stands for," US Attorney General Merrick Garland said in a statement, vowing to "use every available tool" to hold Routh accountable.

Trump has accused the government of mishandling the case, writing in a social media post on Monday that the justice department should “LET FLORIDA HANDLE THE CASE!”

But Garland rebuffed that, telling reporters on Tuesday that his agency will “seek to cooperate and get assistance from” state officials “consistent with the law”.