By Joan Gralla

NEW YORK (Reuters) - Rebuilding at the World Trade Center, site of the September 11 attacks, is behind schedule and over budget, and major problems mean new cost estimates and timetable must be drawn up, officials said on Monday.

Firm projections for the planned memorial, museum, five skyscrapers and transit hub now will be issued by the end of September, New York Gov. David Paterson said.

And it is too soon to say whether the Freedom Tower, which would replace the Twin Towers in the Manhattan skyline, will have to be scaled back, the site's owner said.

The centerpiece of the rebuilding effort, the Freedom Tower had been due for completion in 2011. At 1,776 feet it would be the tallest building in the United States.

Paterson spoke to reporters after the Port Authority of New York and New Jersey, the agency that owns the site, issued a report he commissioned because he feared the projects would take longer and cost more than his predecessors predicted.

Only part of the memorial will be done by the 10th anniversary of the September 11, 2001 attacks. That anniversary had been the previous deadline for unveiling the memorial featuring two reflecting pools marking the outlines of each of the Twin Towers.

However, developer Larry Silverstein said three adjacent skyscrapers on the 16-acre (6.5-hectare) site will be completed on time by 2012.

The project's $14 billion cost keeps rising as commodity prices soar and the 19 federal, state and city agencies that are all involved fail to solve logjams.