The owners of the World Trade Center site announced a delay in the completion of a multibillion-dollar transit hub Thursday but pledged to open a nearly finished Sept. 11 memorial by the 10th anniversary of the terrorist attacks.

They set no firm schedule for the completion of the entire site, which includes four office towers and a performing arts center. The report also said the 1,776-foot Freedom Tower skyscraper has been delayed by up to a year, meaning the signature project of the site won't open until at least 2013.

In a 70-page report on ground zero's tortuous rebuilding process, the Port Authority of New York and New Jersey said the elaborate rail hub will cost $3.2 billion, $700 million more than planned, and should open in 2014, five years after the original projected completion date.

The memorial, "Reflecting Absence," will open on Sept. 11, 2011, with two waterfall-filled pools built in the shape of the twin towers' footprints, and surrounded by the names of nearly 3,000 victims, the report said. But some of the 500 trees in a cobblestoned plaza may not all be planted by that time and a visitor's center may not be open.

The report was issued after Gov. David Paterson ordered a re-evaluation of the rebuilding process in June, saying that there was little clarity about who was responsible for rebuilding the site. He and Mayor Michael Bloomberg had publicly urged the agency to guarantee completion of the memorial by the anniversary.

The report gives certainty to the rebuilding process, Paterson said.

"We know what we are building, how long it will take and how much it will cost," he said.

Bloomberg, who leads the foundation building the memorial, gave only measured support to the pledge to open the memorial on time.

"Fully completing the memorial by the 10th anniversary of 9/11 remains our goal, and this plan doesn't accomplish that," he said.

The Port Authority's executive director, Christopher Ward, said he could not offer a schedule for three office towers being built by developer Larry Silverstein or for the arts center.

The schedule for another office tower under the agency's control would be driven by demand for office space, Ward said. The current financial crisis has made the city's commercial real estate prospects uncertain.

Silverstein said in a statement that he would study the report "to gauge the impact on our part of the World Trade Center rebuilding effort." A lease between Silverstein and the Port Authority requires the developer to give up rights to the towers if he doesn't finish building them in the next five or six years, although there was talk of renegotiating that part of the lease.

An underground Sept. 11 museum should open in 2013, four years later than originally planned, the report said.

Completion of the signature project, the 1,776-foot Freedom Tower now under construction, is about $200 million over budget and will be delayed several months to 2013. Additional parts of the project are also over budget, bringing the final tally to more than $1 billion over estimates.

"While we still face many challenges ahead, we believe we have created a level of certainty and control over this project that has been missing since its inception," Ward said in a letter to Paterson.

The report reflects an understanding of the realities of building from scratch a complex of interconnected skyscrapers, transit links and cultural space in a hole seven stories deep, Ward said, adding that he realized the new deadlines "will be met with a degree of skepticism."

Deadlines for almost every project at the site have changed since plans were first introduced in 2003, and Ward acknowledged the new schedule could also change.

"I cannot promise that we will meet every single milestone every step of the way," he wrote. "This is the most complex construction program in the region's history and setbacks are inevitable."

Most of the report appeared to involve transportation plans, including the rail hub designed by Santiago Calatrava and links to several subway lines, one of which sits in the midst of several construction projects.

The hub's mezzanine will be redesigned, adding columns to an open space. Ward said that the agency considered leaving a temporary hub in place and not building further, but that federal transit funds had been dedicated to Calatrava's design, which is meant to be reminiscent of Grand Central Terminal. The target completion date, 2014, is five years after the hub's original completion date.

Bloomberg, who heads the foundation building the memorial, and foundation officials had pressured the agency to commit to a 10th anniversary opening, saying the public must be able to visit the area by that symbolic date.

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On the Net:

Report available at http://www.panynj.gov