Gov. Gray Davis defended his decision to warn last week of potential rush-hour terrorist attacks against four California suspension bridges, and said he has no intention of easing security on the spans.

Even though the FBI said Tuesday the information that led Davis to issue the warnings was not credible, the governor said he was convinced he made the right move in disclosing the possible threat last Thursday.

"My No. 1 job is to keep Californians safe," Davis said at an economic conference in Los Angeles. "I believe I took the correct steps."

State officials remained on high alert, with California National Guard troops and highway patrol officers continuing to patrol the state's major bridges Tuesday.

"I'm going to err on the side of caution. I'm going to keep the National Guard and the California Highway Patrol on those bridges for the foreseeable future," Davis said.

"We will review the FBI's updated assessment. It's not uncommon for information to change from one day to the next. It may change again. We have those bridges as secure as they have ever been."

U.S. Treasury Secretary Norman Mineta, in Alameda on Tuesday to promote the Sea Marshals program that is helping to protect the nation's ports, said California's bridges remained "vulnerable assets."

"Regardless of whether the threat was bogus or not, they are vulnerable, critical infrastructure to all of us," Mineta said. "There's no deadline on vulnerablity."

Two National Guard troops and a Humvee vehicle were posted around-the-clock Tuesday at each end of San Francisco's Golden Gate and Bay bridges, the Vincent Thomas Bridge at the Port of Los Angeles and San Diego's Coronado Bridge.

"At this point, that's what we're doing — staying in place," said National Guard spokesman Lt. Col. Charles "Terry" Knight.

The FBI said Tuesday in an advisory to law enforcement agencies that the threat to the bridges was not credible.

Davis announced last Thursday that federal officials had "credible evidence" that terrorists might be targeting the four California bridges during the following few days.

The governor was sharply criticized for publicizing the threat, which the FBI said was uncorroborated and should have not been released to the public.

Oakland Mayor Jerry Brown, attending a conference with Davis in Santa Monica, said he would not criticize Davis' decision to warn about the threat.

"What is needed is for state and federal governments to align their strategies in terms of responding to threats of terrorism," Brown said Tuesday.

A warning of an "uncorroborated" threat against West Coast suspension bridges was passed on last Wednesday to law enforcement nationwide as well as 1,700 members of InfraGard, a partnership between the FBI and private companies. Many of these companies then shared the information with their employees.

But the public at large didn't know about the threat until Davis made his announcement Thursday, saying it was based on "credible" information. That surprised federal officials, who nevertheless supported Davis' decision to warn Californians.

The initial warning was based on information provided by U.S. Customs officials, said Matthew McLaughlin, a spokesman for the FBI in Los Angeles.

FBI agents conducting their own investigation determined there was no realistic threat to the bridges, he said.

The California Highway Patrol will have the final say on when the National Guard can stand down from the bridges, said Eric Lamoureux, a spokesman for the Governor's Office of Emergency Services.

"We'll continue to stay on a heightened state of alert in light of the other developments that authorities in Washington have announced," he said.