The shooting attack that killed 14 people in San Bernadino, California, was not the "main thing" the ISIS terror group aims to carry out against Americans, according to terrorism expert Brian Levin.

ISIS is not just "homegrown amatuer lunatics," but it is "a quasi-state apocolyptic terror operation" that could become capable of using weapons of mass destruction, Levin told Lead Stories.

Levin, who directs the Center for the Study of Hate & Extremism at California State University, San Bernardino, said the threat from ISIS and its followers is different from the domestic terrorism perpetrated by white supremacists in the United States.

A chemical weapons attack by ISIS is one scenario, Levin said. While the group may not have that capability today "they may have it later."

"We need a more comprehensive plan from the president" the addresses the military aspect of ISIS. The chaos in Syria is the "staging ground" for terror plotting, he said. "We really had to address that."

Levin's analysis is in line with an intelligence report commissioned by the White House and compiled by analysts working for the director for national intelligence. That secret report "predicts that the self-proclaimed Islamic State will spread worldwide and grow in numbers, unless it suffers a significant loss of territory on the battlefield in Iraq and Syria," according to a report in The Daily Beast.