The Obama administration will announce a new terror alert system "in the coming days," Homeland Security Secretary Jeh Johnson said Monday.

Johnson said the new alert system will better inform the public about threats to the United States, but he did not provide specific details.

This will be the third terror alert system put in place by the Homeland Security Department since the Sept. 11, 2001 terrorist attacks. The much maligned color-coded system was replaced in 2011 by the National Threat Advisory System, which has never been used.

Johnson announced the new alert system during a forum with Defense One magazine. He said the National Threat Advisory System hasn't been used because it requires a "specific, credible threat" to the U.S. in order to be activated. The new effort will include an "intermediate" step, he said.

The plan to change the alert system was announced in the wake of the mass shooting in San Bernardino, California, which the FBI has declared a terrorism investigation. The FBI is investigating the possibility that shooting suspects Syed Farook and Tashfeen Malik were inspired by the Islamic State group to carry out the attacks that killed 14 people attending a holiday luncheon at a social services facility.

Johnson said while a specific motive has not been determined in the California case the threat from home-grown radicals or those inspired by foreign groups is a growing concern in part because such attacks may not be discovered in advance. The new terror alert system, he said, better "reflects the current environment and current realities."

"We need a system that adequately informs the public at large ... about what we are seeing, what we are doing and what we are asking the public to do about it," Johnson said.