President Barack Obama met with the families of most of the San Bernardino shooting victims for nearly three hours, and said he was moved by their emphasis on tolerance following the December 2 attacks.

"As difficult as this time is for them and for the entire community, they also represent the strength and the unity and the love that exists in this community and in this country," Obama told reporters after the meeting.

Fourteen people died in the shootings in San Bernardino, California on December 2, when radicalized Muslims Syed Rizwan Farook and his wife Tashfeen Malik opened fire on Farook's co-workers at a holiday party.

The president and his wife Michelle spent nearly three hours offering their condolences to the family members of victims and first responders in the library of Indian Spring High School, the White House said.

The Obamas, who were greeted on arrival in San Bernardino by Mayor Carey Davis and County Supervisor James Ramos, made the visit on their way to Hawaii, where they will spend the holidays.

On Thursday, federal authorities charged Enrique Marquez with providing material support to Farook and Malik. Marquez allegedly purchased two rifles used in the attack and had plotted to carry out attacks with Farook in 2011.

Federal Bureau of Investigation Director James Comey said on Wednesday there was no indication that Farook or Malik were part of an organized cell or had any contact with overseas militant groups.