Jameson was accused of naming Pier 39, a popular area of San Francisco, as a possible target during communications with an undercover FBI agent posing as an extremist.

He was accused of asking the undercover agent for an assault rifle and equipment for a pipe bomb.

He allegedly said that "Christmas was the perfect day" for an attack, according to local media reports.

Jameson has been discharged from the US Marines for failing to disclose a history of asthma.

During his time in the military he earned a marksmanship qualification, the San Francisco Chronicle reported.