On a day of remembering New York is also preoccupied with the future plans for the Ground Zero site.
A new building, Freedom Tower, will be the centre-piece of a memorial to the victims. But Mayor Michael Bloomburg has complained the work is going “desperately” slowly.
The first steel beams of the new tower were only installed this week.
He says too many people are involved in the decision making process and wants the agency running the project to be replaced.
Bloomburg wants the memorial to be completed in time for the 10th anniversary.
Other ceremonies will take place today at the scenes of the other attacks — the Pentagon and the field near Pittsburgh where the last of the four hijacked planes came down.