The FBI is coordinating a national effort to protect Fourth of July celebrations from potential terrorist attacks, officials said Wednesday.

"We know that terrorists use significant dates and large gatherings as a platform. We want to keep everyone safe," FBI Chicago field office spokesperson David Brown said.

Furthermore, detainees in Guantanamo Bay have expressed a general interest in the day as a time for an attack, officials said on condition of anonymity.

"We are aware that holidays could be targeted," FBI spokesperson Bill Carter said. "We are taking precaution based on that."

As part of the effort, all 56 FBI field offices are required to create plans for monitoring events, especially those near mass-transit systems. Mass-transit areas are of special concern because they gather a large number of people in a small area and for the ease of spreading chemical or biological weapons.

Field offices are also likely electronic surveillance and undercover agents, officials said.

Although no specific warnings have been issued, officials believe terrorists have attempted to strike near holidays before.

Richard Reid is accused of attempting to blow up American Airlines Flight 63 with plastic explosives in his shoes; that flight came just before Christmas. Reid is also accused of working with Al Qaeda in the attempted attack.

Justice Department officials have said they believe additional Al Qaeda operatives are waiting to stage more attacks.

New York's FBI field office is creating plans to monitor July Fourth events, but will not be taking any new or surprising measures, office spokesperson Joe Valiquette said.

"We will not be doing anything that is unusual for major gatherings and holidays in New York. But we will be ready," Valiquette said.

Cheryl Mimura, a spokesperson for the FBI field office in Los Angeles, said a review of the city's scheduled events had not yet been completed.

Bush's Homeland Security office plans on keeping staff at normal levels.

"It's important not to reduce the number of guards simply because it's a national holiday," spokesperson Gordon Johndroe said. "All sections of government must maintain vigilance. For the government, July Fourth will be just another day at the office."

The Associated Press contributed to this report.