NEW YORK (Reuters) - The National September 11 Memorial Museum in New York will not be ready in time for its planned 2012 opening on the 11th anniversary of the attacks, due to a financial dispute between agencies involved in its construction, officials said on Friday.

Arguing over money are the Port Authority of New York and New Jersey, which is overseeing construction at the World Trade Center site in downtown Manhattan, and the National September 11 Memorial Foundation, which designed the museum and raised money for its construction.

The Port Authority says the foundation owes it about $300 million for construction costs, while the foundation says the Port Authority owes it about $146 million because of construction delays.

"There's no chance of it opening on time," Mayor Michael Bloomberg, who chairs the foundation, said on Thursday of the museum. "Work has basically stopped."

More than a million people have visited the National September 11 Memorial, built in the footprints of the twin towers, since it opened on September 12, 2011, the foundation said this week.

The museum is being constructed adjacent to the memorial, much of it set deep below the ground in the cavernous foundations of the towers that were destroyed by hijacked jets on September 11, 2001. It is intended to chart the events leading up to the attacks and their aftermath.

"I think that (the) most important thing about this museum is getting it right," said Joseph Daniels, the foundation's president.

Both sides said on Friday they were working to find a solution, but a revised opening date has not been announced.

"We are working with the city to resolve the issue," Port Authority spokesman Steve Coleman said.

(Editing by Ellen Wulfhorst and Cynthia Johnston)

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[Photo by skinny_lawyer, Creative Commons licensed. Via Wikimedia.]