Alinghi, the top contender in the America's Cup challenger trials, suffered a blow on the eve of semifinal racing today when its mast broke in gusty winds on the final day of practice.

Moments after the Swiss team announced on shore it will use SUI 64, the boat that compiled a 17-3 record in preliminary trials, in Monday's semifinals, the top section of its 110-foot carbon-fiber mast snapped. Skipper Russell Coutts quickly summoned a tow for the 20-mile run back to harbor.

"We have several masts," spokeswoman Veronique Teurlay said. "We've got a backup ready to go and will be ready to sail on schedule." No one was hurt, she said. Winds were up to 27 knots on the Hauraki Gulf.

Alinghi led photographers on a wild goose chase, sending speedy rescue boats off in a false direction to lead the cameramen astray while the injured race boat was towed to a quiet place to clean up the wreckage.

The damage comes 24 hours before top-seeded Alinghi squares off against No. 2 Oracle/BMW in a best-of-seven match. The winner advances to the Louis Vuitton Cup finals in January, while the loser goes to a repechage round against the winner of a second semifinal match between No. 3 and 4 seeds OneWorld and Prada.

Alinghi vs. Oracle is the headline attraction as Coutts and Chris Dickson on Oracle/BMW face off in waters both called home as youngsters. The two Kiwi skippers, both 40, are lifelong rivals. So far Coutts has had the better of the exchange in the Cup, winning twice for New Zealand while Dickson came up short in four attempts for New Zealand, Japan and now the United States. The boats split two races in preliminary rounds here.

The mast problem occurred as SUI 64 and stablemate SUI 75 were two-boat training. Dickson said he was "sorry they broke their mast the day before racing," then added with a chuckle that he wouldn't have minded if it happened a day later.

It's the second mishap of the week for a Cup team. Two days ago two Prada stablemates collided during prestart maneuvering in a simulated race. The damage to the race boat, ITA 74, was serious enough to keep it in the shed on Saturday.

"It's like skiing," Prada skipper Francesco deAngelis said with a shrug. "If you don't crash sometimes you're not trying hard enough."

He said the carbon fiber race boats are "very delicate and the shore crew had a lot of work" repairing damage, but the boat was out practicing again Sunday and will be ready to face OneWorld on Monday.

The OneWorld-Prada matchup, unlike Oracle-Alinghi, is do or die. The winner advances to the repechage round while the loser is eliminated.

OneWorld also awaited results of the second and final day of a five-man arbitration panel's hearings into charges it had illegal documents in its possession during the boat design process. The charges were brought by Prada and Team Dennis Conner, which seek to have OneWorld disqualified.

The resumption of racing brought billionaire Larry Ellison back across the Pacific from California, where he was tending to business as CEO of Oracle software during the break.

The founder of Oracle/BMW said he was pleased as Dickson reeled off 11 straight wins in November. Still, Ellison said, he is nervous. "It's a high-stakes game. You work so hard for so many years, then you find out a lot in the first beat," meaning the first upwind leg of the first race.

Ellison brought Dickson on as skipper after Oracle/BMW had disappointing results in the first round. The move proved costly as Dickson promptly kicked Ellison off the racing team, then swept to 11 wins. Ellison says he does not expect to get back on the boat anytime soon.

"It's unusual enough to have two people sharing the helm," he said, alluding to Dickson's arrangement with helmsman Peter Holmberg. "To have three is ludicrous. So there's no room for me."

Dennis Conner arrives at arbitration hearing, which will determine if OneWorld is disqualified.