NEW YORK » A tall, heavy spire was fully installed atop One World Trade Center today, bringing the New York City structure to its symbolic height of 1,776 feet.

Loud applause and cries of joy erupted from construction workers assembled on a temporary work platform on the roof of the building as the huge, silver spire was gently lowered and secured into place.

“It’s a pretty awesome feeling,” Juan Estevez said from a temporary platform on the roof of the tower where he and other workers watched the milestone.

“It’s a culmination of a tremendous amount of team work … rebuilding the New York City skyline once again,” said Estevez, a project manager for Tishman Construction.

He said the workers around him were “utterly overjoyed.”

Installation of the final two sections of the 408-foot, 758-ton spire was completed after pieces of it had been transported to the roof of the building last week. It will serve as a world-class broadcast antenna.

The building is at the northwest corner of the site where the twin World Trade Center towers were destroyed in the Sept. 11, 2001, terrorist attacks. The 72-story 4 World Trade Center is under construction at the southeast corner of the site.

Lee Ielpi, whose firefighter son died after responding to the attacks, watched workers secure the spire from his office at the nearby 9/11 Tribute Center, which he co-founded.

“The building looks spectacular. … I’m looking forward to the day when the cranes come down and they light the spire at night,” he said. “It’s supposed to be a very moving experience.”

The Port Authority of New York and New Jersey, which owns the site, said the LED-powered light would be activated in the next few months.

“It’s going to have a light that you can see from tens of miles away,” said Port Authority Vice Chairman Scott Rechler. “And that light will change colors and in the next few months we are going to be activating that light, and it will be a beacon of hope just like the Statue of Liberty.”

Today’s final installation, raising the building’s height to 1,776 feet, makes One World Trade Center the tallest skyscraper in the U.S. and third-tallest in the world, although building experts dispute whether the spire is actually an antenna — a crucial distinction in measuring the building’s height.

If it didn’t have the spire, One World Trade Center would be shorter than the Willis Tower in Chicago, which stands at 1,451 feet and currently has the title of tallest building in the U.S., not including its own antennas.

The Council on Tall Buildings and Urban Habitat, a Chicago-based organization considered an authority on such records, says an antenna is something simply added to the top of a tower that can be removed. By contrast, a spire is something that is part of the building’s architectural design.

The tower is slated to open for business in 2014.

New York Gov. Andrew Cuomo and New Jersey Gov. Chris Christie both praised the construction workers for their tireless work.

Tenants include the magazine publisher Conde Nast, the government’s General Services Administration and Vantone Holdings China Center, which will provide business space for international companies.

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Associated Press writer Karen Matthews contributed to this report.