An agreement that paves the way for the completion of a museum commemorating the terrorist attacks of Sept. 11, 2001, has been reach a day before the 11th anniversary of the event, N.Y. Gov. Mario Cuomo says.

Cuomo announced the agreement between the Port Authority of New York and New Jersey and the foundation that controls the National September 11 Memorial & Museum on Monday. The port authority owns the World Trade Centre site.

The underground museum was supposed to open this month, but construction all but ceased a year ago because of a funding squabble between the foundation and the port authority. It will house artifacts including the staircase workers used to escape the attacks.

Almost 4.5 million people have visited the outdoor memorial, which includes a plaza where waterfalls fill the fallen towers' footprints, since it opened last September.

However, even as the agreement was announced critics focused on a new problem: the project's expected $60-million annual operating budget.

The figure comes on top of the $700 million construction cost of the National Sept. 11 Memorial and Museum. A report Sunday by The Associated Press noted $12 million a year would be spent just on security, more than the entire operating budgets of Gettysburg National Military Park and the monument that includes the USS Arizona Memorial at Pearl Harbor, Hawaii.

Mayor Michael Bloomberg, who leads the non-profit foundation's board, on Monday called the Sept. 11 memorial's operating cost a necessity for security and other costs unique to hosting millions of visitors a year on the reborn site of two terror attacks, in 1993 and 2001.

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The museum commemorating the attack on the World Trade Centre in 2001 will finally be completed. (Associated Press file photo )

Some congressional Democrats underscored their efforts to help get federal money to cover some of the operating cost, while a Republican senator reiterated his opposition. Even some victims' family members are divided over whether the annual price tag represents the price of paying tribute to the nearly 3,000 lives lost or the cost of unnecessary grandeur.

At ground zero, several visitors Monday to the memorial plaza were surprised — but not put off — by the $60 million-a-year figure.

"Really?" said Pat Lee, 57, a Walmart manager from Atlanta. But, she said, "I don't think the money is too much, because it's important to keep alive the memory of what happened."

The centrepiece of the rebuilt World Trade Centre site, the memorial includes a serene memorial plaza where waterfalls fill the fallen towers' footprints, and a mostly underground museum that will house such artifacts as the staircase workers used to escape the attacks.

The plaza opened last year and has drawn 4.5 million visitors so far. It was to have been finished by Tuesday, but progress has stopped amid a construction-costs fight between the memorial foundation and the Port Authority of New York and New Jersey, the agency that owns the trade centre site.

The Port Authority has claimed the Sept. 11 memorial foundation owed it $300 million for infrastructure and revised project costs; the foundation has argued it's owed money because of project delays.

The parties involved in the dispute said Monday they had reached an agreement that paved the way for completion of the museum. Even so, it remains unclear how the foundation will cover the costs of running the museum, once it does open.

So far, the foundation has been able to rely on corporate and individual donations and selling memorabilia. The annual expense was about $27.8 million last year, including four months of operating the memorial plaza, according to recently audited financial statements.

But the expense is projected to jump to $60 million after the museum opens. The foundation plans to spend around $12 million a year on private security; operating the waterfalls costs another $4.5 million to $5 million annually, the foundation says.

Foundation officials haven't responded to requests for information about other costs at the site.