Britannia clinched a 5-2 semi-final win over Alinghi in the America's Cup challenger series to secure a place in the Louis Vuitton Cup final in Barcelona.
In the other semi-final, the American Magic kept their hopes alive with a crucial win over Luna Rossa, who suffered dramatic equipment failure during their second race of the day.
"Looks like we've broken the traveller track," Jimmy Spithill, co-helm on the Italian team, said of the damage to a key part of the AC75 foiling monohull's rig, which produced a massive bang and a temporary loss of control when it broke.
The United States are now on three wins, with Italy on four in the first-to-five semi-final. Whoever wins will face the British in the final at the end of the month.
The winner of the Louis Vuitton Cup then gets to challenge defenders New Zealand for the coveted "Auld Mug", which dates back to 1851 and is the oldest international sporting trophy.
Britain under skipper Ben Ainslie had raced to a 4-0 lead, but the less-experienced Swiss crew won a reprieve on Monday.
The Swiss had looked set to cause another upset when they beat the British in the first race on Wednesday, narrowing the gap to 4-2. But they could not capitalise on their improving form in the second race in tricky conditions.
"We are all very relieved to have got through today and to have survived and made it through to the final," Ainslie said on the America's Cup live broadcast after his team's victory on what he described as a "tough day".
"It's seriously hard out here with the wind all over the place," said Ainslie, adding the Swiss were "a great team".
-Reuters