Senior U.S. intelligence officials tell ABC News new intelligence suggests a small al Qaeda cell is on its way to the United States, or may already be here.

The White House has convened an urgent multi-agency meeting for Thursday afternoon to deal with the new threat.

Top intelligence and law enforcement officials have been told to assemble in the Situation Room to report on:

--what steps can be taken to minimize or counter the threat,

--and what steps are being taken to harden security for government buildings and personnel.

Homeland Security Secretary Michael Chertoff told the Chicago Tribune editorial board on Tuesday he had "a gut feeling" that an attack was coming.

"We do worry about whether they are rebuilding their capabilities," Chertoff said. "We strike at them; we degrade them; but they rebuild."

"It suggests they have information that the cell or cells coming this direction want to attack a government facility," Brad Garrett, a former FBI agent and ABC News consultant, said.

Law enforcement officials say the recent failed attacks in London have provided important new clues about possible tactics.


And officials say the London attackers' use of the Internet left important clues that are being used to decode other e-mails that had initially been deemed unimportant but are now taking on new significance.

A senior administration official said the level of concern of a new terror attack is now higher than it has been in some time, and the meeting this week in the situation room is one of a number that have been convened in light of the new intelligence and what happened in London.

White House response:

After the attempted terrorist attacks in the U.K., the U.S. government convened meetings to discuss the situation -- that is what citizens should expect. There is no credible evidence of an imminent threat, however, and counter-terrorism officials regularly meet -- that is not unusual. We are taking all threats seriously and working to ensure we can keep the terrorists from striking at innocent people.