WASHINGTON - (AP) - U.S. counterterrorism officials are chasing anunconfirmed al-Qaida threat to attack New York orWashington in a plot timed to coincide with the 10th anniversary ofthe Sept. 11 attacks.

Officials said the intelligence came in late Wednesday night andindicated al-Qaida planned to use car bombs to blow up bridges ortunnels in New York or Washington. The information also ledintelligence officials to believe that there were three individualsinvolved who were either in the U.S. or planned to travel here.

The threat is being described as specific and credible butunconfirmed.

Security has been ramped up around the country in the weeksleading up to the 10th anniversary, a date officials have longknown al-Qaida viewed as an appealing time to attack. BothWashington, D.C., and New York City are increasing police presence.