NEW YORK -- U.S. Open spectators will encounter tighter security measures, including extra police and a ban on video cameras and backpacks.

Last year's tournament ended two days before the Sept. 11 terrorist attacks.

Each ticketholder will be allowed to bring one bag into the U.S. Tennis Center, where the year's final Grand Slam tournament starts Monday. Bags must be smaller than 12 inches wide, 12 inches high and 16 inches long.

Other barred items include briefcases, coolers, radios, cans and bottles. And security guards can prevent people from carrying any other items deemed dangerous or inappropriate.

Organizers originally announced umbrellas would be banned, too, but later said fans can bring them.

"We have an obligation to protect everybody,'' U.S. Tennis Association spokesman David Newman said Thursday. "We must do everything in our power to have the best security possible.''

Organizers wouldn't say how many uniformed and undercover police are being added.