In one of the more remarkable twists in the tangle of America's Cup events since Australia snatched the gaudy goblet four years ago, Dennis Conner's long-awaited plan for the next regatta was derailed yesterday by a New Zealand plea in a New York court.

Conner's people were all set to disclose terms of the next international gala: A golden summer of racing off San Diego in 1991, with up to 18 foreign challengers from 10 nations competing.

But New Zealander Michael Fay threw a wrench by convincing the New York State Supreme Court to hear his claim that he has the right to race Conner on very different terms: Head-to-head in San Diego next June in huge, $5 million yachts up to 120 feet long on deck.

Conner's Sail America Foundation got the cup when he beat Australia's Kookaburra III on the Indian Ocean last winter, and after a long delay Sail America officials were finally ready to announce terms of the next cup. But late Tuesday New York Justice C. Beauchamp Ciparik issued a temporary restraining order barring the announcement.

Fay contends that instead of giving cup defenders the right to set racing terms, the 100-year-old America's Cup Deed of Gift gives challengers the right to demand a showdown in boats up to twice the size of traditional 12-meters, and the defender has no alternative but to accept.

Conner was not available for comment, but Sail America chairman Malin Burnham, who managed the 1987 Conner campaign, said he expects the claim to be quickly dismissed by the court. "It's a sad day when the America's Cup ends up in this {legal} arena," he said. "The whole thing is a mockery that Michael Fay is trying to make of the cup."

But Fay says he's just following the letter of the deed, which in straightforward if antiquated language gives potential cup challengers the right to demand a three-race showdown with the defender on 10 months notice in boats up to 90 feet long on the waterline, which is exactly what Fay did July 19.

Sail America never responded to the peculiar challenge, but two other cup veterans, Australian Alan Bond and Briton Peter deSavary, also filed challenges for next summer in the huge boats, which could require crews of 35 or more.

Burnham said that, although Fay's challenge might follow the deed's language, it violates the spirit of the multinational, multiple-challenger format that has evolved. He said 18 challengers have filed intent to race in 1991 in 12 meters. If Fay gets his two-boat race, he said, "Ninety percent of those challengers would be eliminated."

Burnham said he expects the court, which became arbiter of cup disputes during the 132 years the New York Yacht Club controlled yachting's top prize, to rule that precedents set over the last several decades changed the terms of the deed. But he conceded that few of the precedents were written into the actual document, and warned that "anything can happen" in court. "If we lose at the first level," he said, "I guarantee we'll appeal."

Should the New Zealanders win in court and the race go on in June, Burnham said Sail America would have a 90-foot-waterline boat ready and "I assure you it'll be a two-boat race."

Fay is already seeing to his half of the possibility. His boat designer, Bruce Farr, a New Zealander with offices in Annapolis, has finished initial drawings and said lay-up work already is under way on a high-tech, lightweight fiberglass hull in Auckland.

The thought of a regatta in boats as big as the immense J-boats used when Vanderbilts and Liptons raced for the cup in the early 1900s is awe-inspiring to some sailors.

"I can just see these things flying downwind in a good blow with three guys cranking up the bulb keel," said Washingtonian Riaz Latifullah, who sailed aboard the unsuccessful U.S. 12-meter Eagle in the last cup. "It's a whole new, neat idea on grand scale, and, with practically no restrictions on design, what's to stop them {designers} from doing anything they want?"

Farr said: "They seem to be trying to ignore us. They may have just lost themselves a month."