NEW YORK — Mayor Rudolph Giuliani said Thursday that the official number of people missing at the World Trade Center had dropped to 5,960 after multiple lists of the victims were double-checked.

The number of missing reported to police had been 6,347 for several days. Giuliani said the revision was made after duplications were found on lists provided by some of the 63 countries that lost people in the trade center attack.

The mayor also said 4,620 names have been registered as missing at a city center for victims' relatives. The correct number — the one many fear will be the true death toll — is likely somewhere between the two, Giuliani said.

Authorities so far have confirmed 305 deaths since two hijacked jetliners brought down the twin 1,350-foot towers Sept. 11.

At ground zero, heavier equipment has been moved in to remove rubble from the 16-acre site. Crews have begun assembling a 420-foot crane that can handle up to 1,000 tons.

Since the attack, 128,050 tons of debris — only about 10 percent of what the Army Corps of Engineers estimates is there — have been removed and taken to a landfill on Staten Island for analysis.

More aggressive removal methods and equipment have not been used because of the search for bodies and survivors. Workers are also combing the wreckage for evidence in the criminal investigation of the attack.

Jim Abadie, the site manager for crane owner Bovis Lend Lease, said the larger pieces of debris hauled out of the wreckage will be trucked to a nearby pier and transported by barge to Staten Island.

Abadie said he has been at the site since the beginning.

``It was chaos,'' he said. ``Now it's controlled chaos.''

As wreckage was pulled away and workers picked through the ruins looking for victims, authorities showed the site to small groups of relatives of those missing or confirmed killed.

At City Hall, Giuliani obtained the support of two of the three mayoral candidates for a plan that would allow him to stay in office for three extra months to help the city recover from the attack.

Democrat Mark Green and Republican Michael Bloomberg agreed to go along with Giuliani's proposal, which would postpone the new mayor's inauguration until April. The mayor is supposed to leave office Dec. 31 under a city term limits law.

Across the rest of the city, some commuters faced their first day of mandatory carpooling. Noncommercial passenger vehicles with only the driver inside were turned back during the morning rush hour, causing some traffic delays. The restrictions were imposed as a way of clearing traffic jams in Manhattan caused by the attack and heightened security.

Higher traffic volume was expected Friday, following the Jewish holiday of Yom Kippur.