September 11 Ground Zero Memorial
The World Trade Center construction site as seen on Sept. 8. A memorial and museum was unveiled at 10th anniversary services on Sunday.

With the tenth anniversary 9/11 fast approaching, U.S. counter-terrorism officials say the threat of a car or truck bomb attack in New York or Washington is "specific, credible but unconfirmed," the New York Times reported Friday.

The Department of Homeland Security said in a statement: "There is specific, credible but unconfirmed threat information. We have taken, and will continue to take all steps necessary to mitigate any threats that arise. As we know from the intelligence gathered from the OBL (Osama bin Laden) raid, AQ (al-Qaida) has shown an interest in important dates and anniversaries, such as 9/11."

New York FBI chief Jan Fedarcyk refused to outline the nature of the threat but hinted it had come from information retrieved from bin Laden's Pakistan compoundwhen he was shot dead in May.

As speculation about the potential security threats are mounts, New York Mayor Michael Bloomberg told the press at a news conference Thursday the police would set up vehicle checkpoints throughout the city, step up bag checks in the subway and keep a close watch on bridges and tunnels.

"We know that terrorists view the anniversary as an opportunity to strike again," said Bloomberg. "Now the threat at this moment has not been corroborated. I want to stress that. It is credible, but it has not been corroborated."

"There is no reason for any of the rest of us to change our daily routines. The best thing we can do to fight terror is to not let it intimidate us," Bloomberg said, adding that there would be no changes to plans for memorial ceremonies.

Security will be at its maximum when President Barak Obama and former President George W. Bush attend a ceremony at the site of the World Trade Center on Sept. 11.

New York Police Commissioner Ray Kelly said that besides measures already in place for the anniversary, police would be taking additional actions and increase their presence by a third, with bomb-sniffing dogs in public places, while tunnels and bridges would be swept for bombs.

Guards will be most visibly deployed at Pennsylvania Station, Times Square and Grand Central stations and people should expect to have their bags checked.

"The public is likely to see and may be inconvenienced by vehicle checkpoints throughout the city," Kelly said.

As rumors of an al-Qaida plot refuse to die down ABC News also reported that three individuals entered the U.S. in August with the objective to carry out a terror attack.

Sources say U.S. officials are also on alert as "chatter" about possible threats have risen in Pakistan.

As the anniversary approaches, U.S. bases raised their alert levels and Pakistani officials have prevented foreign journalists from getting close to the house where bin Laden was shot on 2 May during a secret U.S. raid.

With heightened security and officials and intelligence services on such a high alert, it would be extremely difficult for terrorist cell to successfully bring their terror plans to fruition. While caution is necessary, for years to come the dates Sept. 11 and 2 May will bring focus to potential security threats whether serious or not.