Michael Steven Sandford
Michael Steven Sandford is arrested at the Donald Trump rally in Las VegasDavid Becker/Reuters

A 20-year-old Briton who attempted to assassinate presumptive Republican nominee Donald Trump during a campaign rally in Las Vegas, faces up to 30 years in prison if convicted. Michael Sandford is accused of attempting to grab an officer's weapon to shoot Trump.

According to the Telegraph, Sandford told authorities he drove from California to carry out his attack. Sandford said he had been planning to kill Trump for about a year and he believed he could shoot one to two rounds at Trump before being killed by law enforcement.

Sandford, who has a history of mental health problems, admitted he visited a Las Vegas gun range the day before the 18 June rally to learn how to shoot a gun.

The indictment revealed Sandford had even purchased a ticket to a Trump event in Phoenix, Arizona later that day as a backup plan.

The Surrey native was charged with one count of impeding and disrupting the orderly conduct of government business and official functions and two counts of illegal alien in possession of a firearm by a grand jury, US attorney Daniel Bogden announced. Together the charges mean Sandford could be sentenced up to three decade behind bars. He also faces a fine of up to $750,000.

The Telegraph reported how Sandford's parents, Lynne Standford and Paul Davey, have pleaded for his release. His mother told US Magistrate Judge George Foley that the 20-year-old had previously received treatment for obsessive compulsive disorder and anorexia and once managed to escape a hospital in the UK. Meanwhile, his father said Sandford has Asperger's Syndrome.

Sandford was living illegally in Hoboken, New Jersey after overstaying his visa before moving to the Ontario-San Bernardino area in Southern California, his parents confirmed. "He's been refusing to come back and we were worried about him, we were in contact with the American Embassy," Davey said. "But the American authorities said: 'he's over 18 we can't do anything'".

Davey contends his son must have been coerced or "radicalised" into carrying out the attempted assassination. "He has never mentioned Donald Trump. The reason it is such a shock is because he shows no interest in anything like that," he said. "I doubt he would even know who the president of the United States is."

Sandford will be arraigned on 6 July before US Magistrate Judge Cam Ferenbach, the Las Vegas Review-Journal reported. He has not entered a plea yet, but was denied bail by Judge Foley on the grounds he would be a flight risk.