The foundation has started briefing officials at City Hall, in the office of Gov. George E. Pataki and at the Port Authority of New York and New Jersey, which owns the land. A person involved in meetings about the memorial provided The New York Times with a copy of a confidential foundation memorandum, dated May 2, that summarizes the Bovis findings.

Even before the official release of the new estimate, Mayor Michael R. Bloomberg said yesterday that he had spoken to both Governor Pataki and Gov. Jon S. Corzine of New Jersey about the escalating costs.

"Both governors and I think that $500 million is the amount of money that they're going to have to learn to figure out how to deal with," the mayor said. "We want to build the memorial, but we have to realize that there are conflicting demands in this city."

John P. Cahill, Mr. Pataki's chief of staff, who is overseeing rebuilding at the trade center, issued a statement yesterday saying, "We remain committed to the creation of a prominent, powerful and moving memorial that our nation can be proud of. Generations to come will come to see this tribute. However, we must ensure that it is financially achievable, while remaining consistent" with the original vision.

The report estimates the cost of just the memorial and its related museum at $672 million, up 36 percent from $494 million only four months ago. In addition, the latest projections include $71.5 million for an underground cooling plant, up from $41.5 million four months ago.

Bovis also identified $300 million in site preparations and infrastructure — nearly triple the previous $110 million estimate by the foundation, the Lower Manhattan Development Corporation and the Port Authority — that would be necessary before construction could begin. It contends that the Port Authority must deliver a "buildable site" and should bear those costs.

The authority will almost certainly contest that assertion. Last month it agreed to provide $100 million, based on the prior estimate, as part of a major realignment of the plans to build four major office towers on the site. It also took on financial responsibility for the troubled $2 billion Freedom Tower. Yesterday, some state and Port Authority officials expressed misgivings about the validity of the jump in infrastructure costs, but said that they did not want to say so publicly until they had been briefed.