Homeland Security Secretary Jeh Johnson says he will announce "in the coming days" a new threat warning system.

It would replace the current National Threat Advisory System, or NTAS, which itself replaced the original color-coded system. The problem, Johnson said, is that NTAS is based on having a specific, credible piece of intelligence of a plot.

"We need to get beyond that to go to a new system with an intermediate level," Johnson said. "We need a system that adequately informs the public about what we are seeing."

As an example, he noted that he announced heightened security at federal government buildings a year ago after the shooting attack on the Canadian parliament building in Ottawa, even though there was no known threat of something similar in the US.

"We need to do more of that kind of thing," he said.