Updated

The owners of the World Trade Center site scaled back designs for a multibillion-dollar transit hub Thursday and delayed other projects by several years, but said costs will still be more than $1 billion over budget.

In a 70-page report on ground zero's tortured 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.

The planned memorial to the Sept. 11, 2001, attacks will be finished by the tenth anniversary, the report said, except that some of the 500 trees in a cobblestone plaza may not be planted and a visitor's center may not be open. Gov. David Paterson and Mayor Michael Bloomberg had publicly urged the agency to guarantee completion by the anniversary.

An underground Sept. 11 museum should open in 2013, four years after that segment's initial completion date.

Completion of the signature project, a 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.

The agency did not set schedules for four other office towers planned for the site or for a performing arts center, and did not issue a final budget for the memorial.

"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," the agency's executive director, Christopher Ward, said in a letter to Paterson.

Ward said 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. He said 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.

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 seemed 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.