Security is heightened at major West Coast bridges after the FBI issued a terrorism alert for the next few days.

Officials in eight western states received warning that terrorists may be planning rush-hour attacks between Friday and Wednesday, the Justice Department confirmed.

The confirmation comes after a warning Thursday from California Gov. Gray Davis, who said law enforcement officials had "credible evidence" that four California bridges, including San Francisco's Golden Gate Bridge, might be targets.

The alert was also sent to law enforcement agencies in Washington, Oregon, Arizona, Nevada, Utah, Montana and Idaho on Wednesday.

Federal officials supported Davis' decision to reveal the potential threats, but they didn't make the information public until after he spoke out.

"I respect the decision Governor Davis made; he exercised his judgment," said Homeland Security Director Tom Ridge. "Had he chosen not to reveal, I would have respected that as well."

President Bush sounded the same theme Friday. "As a former governor, I didn't particularly care when the federal government tried to tell me how to do my business." He said governors "should be able to conduct their business the way they see fit."

Davis told The Associated Press he felt he had an obligation to make the announcement.

"This threat came from three separate federal sources. It was specific, it was time-sensitive, and I feel an obligation to share that information with Californians," Davis said. "If I failed to share that information and, God forbid, something went wrong, I'd be kicking myself."

The FBI message said: "Reportedly, unspecified groups are targeting suspension bridges on the West Coast."

Six "incidents" were believed to be planned, the FBI alert said. Davis said reports from other federal agencies suggested the attacks were planned sometime between Friday and Nov. 17, the beginning of the Muslim holy month of Ramadan.

Although hundreds of threats have been called in to authorities around California since the Sept. 11 terrorist attacks, this is only the second judged credible enough to issue an alert, Davis said.

Justice Department spokeswoman Mindy Tucker said the information that prompted the warning was "at a lower level" than the reports that led authorities to alert the general public Monday of the possibility of an attack sometime this week.

A senior U.S. official, speaking on condition of anonymity, said the threat is based on new information acquired by U.S. intelligence and law enforcement since Monday's warning. The official said a foreign Islamic terrorist group may be targeting the bridges.

The California bridges identified by Davis as possible targets were San Francisco's Golden Gate and Bay bridges, the Vincent Thomas Bridge at the Port of Los Angeles and San Diego's Coronado Bridge.

Sen. Dianne Feinstein, D-Calif., said after speaking with FBI Director Robert Mueller that she supports the governor's decision.

"I talked to the director of the FBI and he didn't walk away from it," she said of the potential threats.

Ridge said there is no "universal blueprint" for deciding whether to release terrorism information. Federal authorities "thought it was important enough to relate to the governor, and the governor thought it was important enough to relate to his citizens," he said.

Davis said security around the bridges has been heightened since the Sept. 11 terrorist attacks in New York and Washington. The extra security includes flyovers and an increased presence by the California Highway Patrol and U.S. Coast Guard, he said.

After Wednesday's alert, the governor said National Guard troops had also been posted at both ends of the bridges.

"We feel we're well-prepared for any nefarious and criminal actions," said Jeff Weiss, spokesman for the San Francisco-Oakland Bay Bridge. "We're routinely inspecting the IDs of workers ... on the bridge to assure that everyone who is on the bridge belongs on the bridge."

California Highway Patrol Commissioner Spike Helmick stressed that the public shouldn't be fearful.

"Those bridges are safe. We encourage people to use them. In fact, I'll be driving over them tomorrow on several occasions," Helmick said.

Arizona authorities said no specific threat had been received there. "Our law enforcement has been on high alert and continues to be on high alert," said Francie Noyes, a spokeswoman for Arizona Gov. Jane Hull.

Officials in Oregon and Washington said the alert had triggered additional security precautions at some of the most heavily traveled bridges, including Washington's Tacoma Narrows Bridge. Oregon Gov. John Kitzhaber said the Coast Guard would be checking underneath his state's bridges more often and he urged people not to be afraid.

"It would be an unfortunate victory we would hand them if people simply stopped driving," Kitzhaber said.

In San Francisco, tourists Sharon and Jeff Forrest of Bloomfield Hills, Mich., were strolling across the Golden Gate Bridge about the time Davis was making his announcement. They said it wouldn't have deterred them.

"It wouldn't change our plans at all," said Sharon Forrest. "There was a lot of security on the bridge and we noticed the Coast Guard under the bridge. As far as we're concerned, you just keep doing what you're going to do."

Officials representing the agencies that operate the bridges said they are taking the threats seriously.

Janet Vuoso, who lives near Los Angeles' Vincent Thomas Bridge, said she is concerned about her family's safety.

"I'm going to go home and tell my daughter to stay away from the bridge," said Vuoso, who teaches at a private medical school. "I don't think it's a question of if, but a question of when."

The Associated Press contributed to this report.