Team New Zealand could be left with no one to play with in the lead-up to the 2000 America's Cup.
Skipper Russell Coutts is puzzled over why some of the challengers want to ban pre-Cup sparring with the defenders.
Coutts said last night that two syndicates were circulating a petitionto stop all the challengers holding practice races against Team New Zealand before the regatta in February 2000.
Coutts would not say who the two challengers were, but said neither had won the America's Cup before.
Two of the syndicates who are in Auckland - America True and Prada Italy - said they had not seen the petition but had heard about it.
The attempted boycott does not involve next week's Road to the America's Cup regatta because that is raced in identical boats.
While it may seem logical that challengers would want to deny the defenders even the slightest advantage, New Zealand challengers have always sought sparring partners or helped others out in their America's Cup history.
In 1987, the beaten KZ7 raced against Australian defender Kookaburra III after the challenger series to try to keep the Cup Down Under.
"In 1992 we spent some time with Dennis Conner, and last time we hooked up with Young America," Coutts said.
"This is an interesting one. It can work both ways - they could learn something of us, too.
"I guess our policy hasn't changed - we would like to race against someone."
If the protocol goes ahead, Team New Zealand will have to continue racing among themselves - the drawback of being the only defender.
America True head and skipper Dawn Riley said it came as no surprise that some challengers wanted to keep their secrets away from Team New Zealand, whether it was on old or new boats.
"Challengers and defenders don't usually race against each other," she said. "But this is the first time someone's tried to put it down in writing.
"We've heard about it but we're not party to it. If it comes to us, we probably would sign it, though.
"But if just one challenger doesn't sign, then it holds no weight."
