New York, Jan 1 - Hundreds of thousands of New Year's Eve devotees braved freezing temperatures and snow mixed with cold rain waiting to watch the ritual dropping of the crystal ball announcing 2010 in Times Square.

Hundreds of New York City's police and armed troops were deployed to provide security in and around the tourist-must-see Times Square Thursday night.

Barricades went up early Thursday, blocking traffic from the main plaza where all eyes will watch Times Square No. 1 building and the ball descending on top of a pole 60 seconds before midnight (0500 GMT).

Security was tight. In addition to armed troops deployed in the vast subway network serving the city's 8.5 million residents, others were sent to the city's two main airports La Guardia and JFK International Airport.

With the recent bombing attempt on a US airliner on Christmas Day, nerves were especially on edge and the airspace over Manhattan was tightly patrolled by police helicopters.

Police, who locked down Times Square, were also equipped with radiation and biological detectors.

Security measures were strict. Revelers bundled with heavy winter coats were not allowed to carry backpacks or large bags into barricaded areas. Those who would leave before the dropping of the ball were prevented from returning to their original site and alcoholic beverages were banned.

City Hall officials, led by Mayor Michael Bloomberg, who was sworn in Thursday for a third, four-year term, were joined by selected students from 12 public schools ranked among the 100 best in the US, media reports said.

This year's ball with 2,600 Waterford crystals were lit up with LED lights. The crystals designed with interlocking ribbon patterns woven into a Celtic knot called Let There Be Courage. The knot in different colours have been also used in anti-AIDS campaign and to welcome home the troops.

The mass of revelers was expected to leave behind more than 40 tonnes of debris, including party hats, noisemakers, confetti, and streamers.

For this reason, the city had planned to send 150 sanitation sweepers immediately after Thursday midnight, armed with mechanical sweepers, trucks and leaf blowers to clean up Times Square for tourists on New Year's Day.

"We generally have the place cleaned up early in the morning," Bernard Sullivan, an official of the department of sanitation, told a local news broadcast.

"There might be some tidying up on the side streets that continues through the morning, and we have people in place to go right through tomorrow to make sure everything is in tip-top shape," he said.

But the bad weather in New York dampened prospects of a "blue moon" over Times Square on New Year's Eve.

Weather forcasters and astronomers said this week that a blue moon was to add to the New Year's Eve celebrations in most of the world.

The blue moon phenomenon occurs when there are two full moons within a month, which happens every two and a half years. The last full moon was in Dec 2. But a blue moon, which has nothing to do with colour, is rare on New Year's Eve. (dpa)