Alinghi's lawyers contended that the San Francisco club's July challenge on behalf of BMW Oracle Racing was invalid because it failed to properly describe the yachts in which the race would be sailed.

The challenge letter described a boat that would measure 27 metres long by 27 metres wide - a dimension that could apply only to a multihulled vessel like the catamaran that American Dennis Connor used to defend the cup in 1988.

The challenge, however, also called the boat a "keel yacht," a term traditionally used to describe a boat with one hull.

Alinghi argued in court papers, filed in state court in New York on Thursday, that BMW Oracle's bid should be tossed because it proposes a boat that doesn't exist, or would be so misshapen because of its bargelike dimensions that it would be unfit for racing.

The Golden Gate Yacht Club said Alinghi's new claim lacks merit.

"If these arguments were valid they would have been presented months ago," BMW Oracle spokesman Tom Ehman said.

In November, a New York judge disqualified Alinghi's favored Spanish challenger, Desafio Espanol, of Club Nautico Espanol de Vela, on the grounds that the new club hadn't previously held a major regatta, as required by the cup's deed of gift.

The two sides are due back in court in January.