The rebuilding of the World Trade Center site is over budget and years behind schedule _ including the Sept. 11 memorial that was once expected to open on the 10th anniversary of the terrorist attacks.

Christopher Ward, executive director of the Port Authority of New York and New Jersey, which owns the site, issued a report on Monday with more than a dozen issues slowing rebuilding and raising costs, including an over-budget transit hub, the uncertain pace of dismantling a condemned tower where another is planned and construction of several projects around a working city subway line.

"The schedule and cost estimates for the rebuilding effort that have been communicated to the public are not realistic," Ward wrote to Gov. David Paterson.

He said a committee of developers and agencies would set new "clear and achievable" timelines by September. He said plans to build five office towers, a $2 billion-plus transit hub, a Sept. 11 memorial and a performing arts center would be completed, although "the question is when and for how much."

But Paterson said later Monday that the Port Authority "will come back and alert us if they feel that perhaps the project is planned beyond our ability to perform," and Mayor Michael Bloomberg suggested that Spanish architect Santiago Calatrava's design for the transit hub, budgeted between $2.2 billion and $3.4 billion, was too expensive to be built.

"Whether we can afford the Calatrava design, which was spectacular, I don't know," the mayor said. "That's the last piece and the most problematic because there is no money for it."

Ward said that the Sept. 11 museum also would not open on the 10th anniversary of the 2001 attacks. Other projects on the site were scheduled to open by 2013, although the performing arts center never had a construction plan.

The report ordered by Paterson _ the third governor to push for speedy development of a 16-acre site where a temporary train station is the only completed project in seven years _ suggested that the earliest estimates just after the attacks for rebuilding ground zero weren't truthful.

Ward called the estimates, most issued during Gov. George Pataki's administration, "emotional dates," and Paterson promised that in the future, "we will tell the truth every step of the way" about the project.

Pataki once predicted that steel for the 1,776-foot Freedom Tower, the tallest skyscraper planned for the site, would be up by 2006. Steel has just risen above street level for the tower, last estimated to open in 2013.

"Did we set aggressive timetables? Absolutely," Pataki spokesman David Catalfamo said Monday, adding that they were based on engineers' estimates at the time. "All the same people who are there now were there then."

Several other lawmakers blasted the pace of a project that has been slowed by political wrangling between the city and state, passionate arguments about the site's symbolism and the logistics of building so much at once on a small space.

"This has become an international embarrassment," said Manhattan Borough President Scott Stringer. "You could not even make this up."

U.S. Sen. Charles Schumer said: "After seven years of Alice in Wonderland fantasy plans, it's refreshing to finally be presented with a no-nonsense, realistic look at the challenges to progress at ground zero."

Ward listed 15 issues affecting the rebuilding, which he said didn't become clear until full-scale construction began on most projects over the past three years.

The transit hub, featuring Calatrava's elaborate winged dome, presents some of the greatest rebuilding obstacles because it affects office towers, the memorial and space for an arts center that surrounds it. Completion estimates have gone from 2009 to 2013 over the past year.

Ward said the Port Authority is working on several options to cut costs, including redesigning the dome so that its roof does not open and close as once designed.

Other issues include part of a city subway line that runs in the middle of several of the projects, a land deal that hasn't been completed to relocate a Greek Orthodox church near the site and the protracted dismantling of a condemned ground zero tower where one of the skyscrapers is slated to be built, he said.

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Associated Press writer Deepti Hajela contributed to this report.