A British man who attempted to kill Donald Trump is facing up to 30 years in prison after a grand jury in Las Vegas decided to charge him.

Michael Sandford, 20, is accused of trying to grab a police officer's gun to shoot the presumptive Republican presidential nominee at a campaign rally in the city.

Sandford, who has a history of mental health problems, told police he drove from California to kill Mr Trump, and he went to a Las Vegas gun range to learn to shoot the day before the June 18 rally.

Daniel Bogden, US attorney, said the grand jury charged Dorking-born Sandford with disrupting an official function and two firearms counts that, together, could sentence him to up to 30 years in prison.

His parents have pleaded for him to be released, with his mother Lynne telling Federal Magistrate Judge George Foley that her son was treated for obsessive compulsive disorder and anorexia when he was younger, and once escaped a hospital in England.