A major Christmas Day terror attack on San Francisco’s famous Pier 39 by a former marine has been stopped after an undercover operation by FBI agents.

Everitt Aaron Jameson, 26, a Modesto tow-truck driver, was charged Friday (local time) with attempting to provide material support to a foreign terrorist organisation.

According to an FBI affidavit, Jameson told an undercover agent he believed to be associated with senior leadership of the Islamic State group that he wanted to conduct a violent attack on Pier 39, which is packed with restaurants, bars and souvenir shops, because it is heavily crowded.

He told the undercover agent that Christmas Day would be “the perfect day to commit the attack” and that he “did not need an escape plan because he was ready to die,” the affidavit said.

He asked for help obtaining a fully automatic military assault rifle, either an M-16 or an AK-47, along with ammunition and materials to make explosives, including nails, timers and remote detonators, the affidavit said.

Pier 39 was the target of the Christmas Day attack. Photo: AAP

However, Jameson told the undercover agent Monday that he had reconsidered and felt he could not carry out the attack after all, the affidavit says.

A martyrdom letter and several guns were found in the home of the former marine, according to the FBI.

He denied the allegations during a hearing in the federal court Friday.

His father, Gordon Jameson, said he believes the FBI has the facts wrong.

“He wouldn’t do that to innocent people,” the elder Jameson told the Merced Sun-Star .

“He’s a loving, kind person that would never hurt nobody.”

Everitt Jameson as a Marine, before being discharged for not telling the truth about his asthma. He was arrested by the FBI for allegedly planning to attack Pier 39 on Christmas week https://t.co/gvCkeZcIkz pic.twitter.com/IV7Q1Zf3t8

— KTVU (@KTVU) December 22, 2017

Everitt Jameson was under surveillance and “the public was never in imminent danger,” FBI spokeswoman Katherine Zackel said in a statement.

She and San Francisco Acting Mayor London Breed both said there are no other known threats, though police increased their presence throughout the city after being notified of the FBI investigation several days ago.

Here is my statement on the FBI's investigation on the threats against our City. pic.twitter.com/4Br7mJ1wZu

— London Breed (@LondonBreed) December 22, 2017

“San Francisco is a city that proudly champions democracy, freedom and liberty. Sadly, that makes our home a target,” Breed said in a statement.

“We will not allow the thwarted attempts of one dangerous individual to disrupt our way of life. We will remain vigilant and continue to protect our city from any threat.”