Authorities have arrested a man who was walking the grounds and appeared to be monitoring security planning at Donald Trump’s California golf course ahead of the US President’s visit.

The Los Angeles County Sheriff’s Department said Jeanine John Taele, 38, was taking photos and video and had a 16-round magazine with ammunition in his pocket.

Authorities recovered a loaded pistol in his car. Law enforcement searched his home in the nearby city of Downey on Monday and found a plethora of firearms, magazines and ammunition, body armour and notebooks with “concerning statements”.

The sheriff’s department announced Sunday’s arrest as Trump was preparing to arrive for the Republican National Committee dinner at the Trump National Golf Course in the suburb of Rancho Palos Verdes just south of Los Angeles.

Taele was charged with several crimes including second-degree robbery, receiving a large-capacity magazine and possession of a short-barrelled rifle or shotgun.

He was also charged with carrying a concealed firearm in a vehicle, a misdemeanour.

He pleaded not guilty to all the charges and was ordered to stay away from the golf course and not possess weapons. His bail was set at $US250,000 ($A354,000).

It wasn’t clear if he had a lawyer and family members could not immediately be reached for comment.

The sheriff’s department said when they made contact with Taele on Sunday, they had determined he was being investigated by the El Segundo Police Department for robbery.

The sheriff’s department said there is “no credible threat to our communities”.

A jury in 2025 found a man guilty of trying to assassinate Trump at the President’s Florida country club.