Nothing may underscore more strongly the need for a federal office dedicated to making the country safe from terrorist attacks than the FBI's warning that the enemy may strike again soon.

"Certain information, while not specific as to target, gives the government reason to believe that there may be additional terrorist attacks within the United States and against U.S. interests overseas over the next several days. The FBI has again alerted all local law enforcement to be on the highest alert and we call on all people to immediately notify the FBI and local law enforcement of any unusual or suspicious activity," the FBI said in a statement released Thursday afternoon.

An FBI spokeswoman said the warning is based on information from "a pretty compelling source" received since Monday.

It's not the first threat the FBI has received since the Sept. 11 attacks on the World Trade Center and Pentagon, but it is the first time the bureau is warning the public.

The threat lends weight to a proposal offered by Sens. Joe Lieberman, D-Conn., and Arlen Spector, R-Penn., Thursday that would make permanent the Office of Homeland Security, created by President Bush shortly after the Sept. 11 attack. Former Pennsylvania Gov. Tom Ridge officially began his duties as head of the office this week.

Lieberman told reporters that the legislation would bring the Federal Emergency Management Agency, the Customs Service, the Border Patrol, the Coast Guard, and other offices responsible for critical infrastructure under the same bureaucratic umbrella.

He said he wanted to make sure the new office had teeth.

"I don't think he's been given all of the tools he needs to get this job done," Lieberman said of Ridge. "We need a robust executive agency to carry out the core functions of homeland defense. That is the goal of the legislation we are introducing."

The legislation will elevate the office to a cabinet-level agency, which will ensure it fiscal budget authority, and protection from becoming a political football in the future between competing agencies.

"As a practical matter, it is impossible for Gov. Ridge to go to the president every time there is a turf battle," said Spector.

Both senators said they would reassess the legislation if the president opposed the idea, but felt there was a growing sense in both political parties that the office must have the resources to fight the war on terrorism.

Reps. William "Mac" Thornberry, R-Texas, and Ellen Tauscher, D-Calif., introduced a similar measure in the House.

Fox News' Kelley Beaucar contributed to this report.

Catherine Herridge is an award-winning Chief Intelligence correspondent for FOX News Channel (FNC) based in Washington, D.C. She covers intelligence, the Justice Department and the Department of Homeland Security. Herridge joined FNC in 1996 as a London-based correspondent.