The New York-New Jersey Port Authority on Monday said the World Trade Center developer, Larry Silverstein, had stopped negotiating over his demand for the agency to guarantee his loans for two office towers.

Silverstein and the Port Authority, which owns the site, have had numerous clashes. In 2006, they negotiated a so-called master development agreement, which requires them to settle differences via arbitration. Silverstein has now sent the agency a notice beginning arbitration.

But the Port Authority said the arbitrators cannot settle this financing dispute. Silverstein is seeking unspecified compensatory damages based on his claim that the authority will miss its deadlines for the vehicle security center and the new mass transit hub, an agency official said by telephone.

(Reporting by Joan Gralla; Editing by Dan Grebler)