Weapons confiscated from last Wednesday's attack in San Bernardino, California are shown in this San Bernardino County Sheriff Department handout photo on December 3, 2015. [Photo/Agencies]

WASHINGTON/LOS ANGELES - A former neighbor suspected of supplying guns to the married couple who massacred 14 people in San Bernardino, California, was charged on Thursday with conspiring to provide material support to terrorists, the US Justice Department said.

Enrique Marquez, 24, a friend of Syed Rizwan Farook, 28, who launched the Islamic State-inspired attack on Dec. 2 with his wife, Tashfeen Malik, 29, also told investigators he and Farook plotted earlier mass casualty attacks, prosecutors said.

US Attorney Eileen Decker said the two men conspired to commit "vicious" assaults on targets including a California community college and a state highway during rush hour.

"Even though these plans were not carried out, Mr. Marquez's criminal conduct deeply affected San Bernardino ... and the entire United States when the guns purchased by Marquez were used to kill 14 innocent people and wound many others," Decker said in a written statement.

Decker said there was no evidence that Marquez took part in Dec. 2 attack or had prior knowledge of it. He was arrested on Thursday, authorities said, and was expected to make an initial appearance in federal court later on Thursday.

According to an affidavit filed by prosecutors, the two men met in 2005 when Marquez became Farook's neighbor in Riverside, California.

Farook introduced Marquez to radical Islamist ideology, prosecutors said, and by 2011 Marquez was spending most of his time at Farook's home listening to lectures and watching videos with extremist content.

At that point, the pair began planning gun and bomb attacks, the affidavit said, and Marquez told investigators their targets included the library or cafeteria at Riverside Community College, where they had both been students.