NEW YORK — 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.
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 planned memorial to the attacks will be finished by Sept. 11, 2011, 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.
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, he said.
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.
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,’’ 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.