Luna Rossa Prada Pirelli bounced back superbly after a nosedive to keep the Louis Vuitton Cup final clash with Ineos Britannia tied at 4-4 on Tuesday.

The Italians were forced to retire from the first race of the day but after their boat was patched up they produced a superb display to stay neck-and-neck in the battle to reach the 37th America's Cup final.

The winner of the first-to-seven final will face double defending champions Emirates Team New Zealand later in October in Barcelona.

"These curveballs that keep coming our way, that's when you seen a champion team," said Luna Rossa helmsman Jimmy Spithill after his team's victory.

"The shore team were able to get us out there and (it was an) absolutely flawless race.

"We're sort of making a habit of this, it's good to know the team can take that pressure when it comes on. Well done to the whole team."

In the first race the British boat got off to a strong start at the cross but the Italians were hot on their tail.

They broke away from the first gate in opposite directions, both at high speed, but the Italians endured a dramatic nosedive and stopped racing.

Britannia continued conservatively and claimed a 4-3 lead midway through the fifth leg when the stranded Italians eventually decided to retire.

"We had a problem at the top mark and we stuffed the bow in the water and had a lot of water come on deck, so we lost the instruments and part of the fairing," explained Luna Rossa helmsman Francesco Bruni.

The Luna Rossa shore team were able to fix the damage caused by the nosedive and the 'Silver Bullet' was ready for the eighth race of the final.

Ineos lost control on the boundary and were issued a penalty which allowed Luna Rossa to take control in the first leg.

The Italians made no mistakes as they retained a small advantage on the British boat throughout and secured victory by 16 seconds.

"We just got out of position, in these conditions it's really hard... it was our mistake and they did a great job to defend us, a close race," said Ineos skipper Ben Ainslie.

"Just got to keep pushing hard, (these are) two good teams going at it hammer and tongs."