The project's initial $14bn (£7bn) budget has continued to rise
The owner of the World Trade Center has abandoned the timetable for rebuilding work at the site of the 9/11 attacks, saying it was "not realistic".
Port Authority of New York and New Jersey executive director, Christopher Ward, listed over a dozen issues that had slowed work and raised costs.
New dates for the completion of a memorial, skyscrapers and a transit hub are expected to be issued in September.
It is unclear if the centrepiece Freedom Tower will now be scaled back.
The tower, intended as a replacement for the destroyed Twin Towers, had been scheduled for completion in 2006 and then 2011, but the latest estimate is 2013.
At 1,776ft (541m) it would be one of the tallest buildings in the world.
In a report to New York governor David Paterson, Mr Ward said: "The schedule and cost estimates of the rebuilding effort that have been communicated to the public are not realistic."
He said developers and government agencies would set new "clear and achievable timelines" by the end of September.
Mr Ward said the earliest rebuilding estimates in the wake of the 9/11 attacks were not truthful, referring to them as "emotional dates".
The deadlines for the redevelopment work have been moved several times.
The project's initial $14bn (£7bn) budget has continued to rise as commodity prices soar and developers and government agencies wrangle over site plans.