NEW YORK (AP) - The silver spire topping New York City's One World Trade Centre has been fully installed on the building's roof. That brings the iconic structure to its full, symbolic height of 1,776 feet (541m).

The Port Authority of New York and New Jersey says the spire's installation was completed on Friday morning.

The height of 1,776 feet is symbolic of the year 1776, when the US declared its independence.

Pieces of the spire were transported to the roof of the building last week. It weighs 758 tonnes.

The 408-foot (124m) spire will serve as a world-class broadcast antenna. An LED-powered light emanating from it will be seen from miles away.

The new tower is at the northwest corner of the World Trade Centre site, which is well on its way to reconstruction with the 72-storey Four World Trade Center and other buildings.