We have an obligation to those left behind to continue the rebuilding that has already started

Michael Bloomberg

A ceremony to mark the event will be held on the site of the fallen World Trade Center towers in lower Manhattan.

Mr Bloomberg said some efforts to recover human remains would continue beyond that date, but the ceremony - which will begin at the precise time of day that the second tower collapsed - would provide "symbolic closure".

The ceremony will include the removal of an empty, flag-draped stretcher symbolising victims whose bodies were never recovered.

Latest figures put the number of people confirmed dead or missing after the attack at 2,823.

Only 1,000 of the 2,800 victims have been identified so far

Work at the World Trade Center site - now known as "Ground Zero" will finish three months ahead of the schedule originally set by city officials, and at a fraction of the cost.

It had been believed that as much as $7bn would have to be spent to clear the rubble, but it has turned out to be more like $750m.

Eight months ago the work began by hand, with rescue workers filling buckets as they clambered over the debris.

They called out constantly, in the hope for finding survivors.

But the last person to be rescued alive from the pile of concrete and twisted steel came out a day after the attacks.

Since then, work with heavy lifting gear has continued around the clock, stopping only for brief pauses in remembrance for the victims.

Whenever the remains of a victim were unearthed, workers stood at attention as the body was carried out, draped in the US flag.