PASADENA, Calif. (AP) _ Security will be extra tight at this year's New Year's celebrations around the country, with military helicopters patrolling over the Rose Parade, Times Square and the Las Vegas Strip.

``I think the level of security this time around within the United States is absolutely unprecedented,'' Homeland Security Secretary Tom Ridge said on CBS's ``The Early Show.''

As revelers prepare for New Year's Eve, the nation's terrorism alert is at its second-highest level, though officials said there were no specific threats against the holiday gatherings and urged people to go ahead with their plans.

In Las Vegas, where 300,000 revelers are expected on the Strip, officials announced armed military helicopters will fly overhead.

Jerry Bussell, Nevada Gov. Kenny Guinn's adviser on homeland security, said military helicopters will also be used in New York City, Los Angeles, Washington and other cities with big outdoor gatherings.

``These aircraft are equipped to dismantle or disrupt any kind of ground attack,'' said Sheriff Bill Young, ``and also other aircraft that would attempt to fly into our airspace.''

Sharpshooters will be posted on hotel-casino roofs, and streets will be blocked off with concrete barricades, Young said. Sightseeing helicopters will be grounded from 9 p.m. New Year's Eve to 3 a.m.

In Pasadena, where thousands gather along the 5 1/2-mile Rose Parade route and attend the Rose Bowl football game on New Year's Day, video surveillance cameras will watch the spectators lining the streets.

Flights over the Rose Bowl will be limited to police and military aircraft, and everyone working in the stadium, from hot-dog vendors to TV camera crews, will be required to wear photo IDs.

``We decided not to live our lives in fear, and do what we want to do,'' said Janet Powles, 60, of Rapid City, S.D., as she watched volunteers apply flower petals to Rose Parade floats.

In Las Vegas, however, terror concerns apparently affected hotel bookings. Deutsche Bank analyst Marc Falcone said New Year's Eve cancellations jumped in the past week and were running twice as high as last year.

In New York City, the New Year's Eve preparations included flight restrictions and military helicopter patrols over Times Square.

Police Commissioner Ray Kelly said that there will be more officers on duty this year than last, and that they will focus more heavily on hotels, landmarks and ferry terminals. He would not disclose numbers.

Organizers said they expect this year's crowd to be larger than last year's gathering of 750,000.

Manhole covers are being sealed shut in Times Square, and mailboxes, trash cans and newspaper boxes are being removed. Plainclothes officers will mingle with the crowds, and elite counterterror teams will have equipment to detect chemical, biological or radiological contamination.

Mayor Michael Bloomberg said the city was well-protected.

``Sadly, terrorism is something that we have to live with,'' he said. ``Leave the worrying to the professionals.''

In cities such as Columbus, Ohio, authorities urged people to be watchful.

``Because of the code orange, we're asking people to be extra alert and asking anyone who sees anything odd to talk to an officer,'' said police Lt. Karl Barth. ``There will be a lot of officers around.''

In New Orleans, security officials implemented a new game plan for the Sugar Bowl, where Oklahoma and Louisiana State University will play for college football's Bowl Championship Series title game on Sunday.

Superdome parking garages will be closed and a fence will be put up around the dome. Some streets will be closed.