- The 34th edition of sailing's America's Cup begins in San Francisco Saturday
- Defending champions Oracle Team USA face Emirates Team New Zealand in the best-of-17-races series
- Oracle Team USA have been deducted two points for illegally modifying boats
- U.S. skipper Jimmy Spithill says his team are the underdogs
It has been a stormy start to the America's Cup for the defending U.S. champions -- and the boats have yet to leave the safety of San Francisco Bay.
The 34th edition of the world's oldest sporting event begins Saturday with Oracle Team USA already trailing their New Zealand challengers.
The Oracle race team has been docked two points for illegally modifying its catamarans by adding lead and resin weights and lengthening the vessel's main king posts.
The U.S. team was also fined $250,000 and had three crew members banned just four days before the start of the competition.
"There's no question in my mind that Team New Zealand are the favorites here," said Oracle's Australian skipper Jimmy Spithill. "We're in an underdog position now.
"We have to go out and win races. We have to get out there and take one race at a time. That doesn't really change."
An international jury of sailing experts explained the punishment in a detailed statement, saying: "The jury holds the view that each of the modifications were made in the belief that they would enhance performance.
"The seriousness of the breaches cannot be understated.
"The jury considers that to adequately reflect the seriousness of the matter, to emphasize to competitors and sailors there is an absolute obligation to comply with class rules, a penalty involving racing in the match in addition to a substantial fine is appropriate."
The punishment means Oracle Team USA will now have to win 11 races in the best of 17 series to retain the America's Cup.
To whisk the trophy away to New Zealand waters, the Emirates Team must win nine races-- the highest victory margin in the Cup's history.
Homegrown New Zealand skipper Dean Barker commented on the penalty: "The decision changes nothing for us. I think it's good the matter is out of the way and we can get on and go racing."
The America's Cup can claim to be even older than the modern Olympics. Sailors first took to the waters to fight for the "Auld Mug" in 1851.
The competition began when a group of New York businessmen sailed to England and won a race around the Isle of Wight.
The America's Cup has now returned to U.S. waters for the first time in 18 years and, despite its rich traditions, sailing's elite team event has introduced several modernisations.
For the first time, the teams will race inshore rather than offshore, battling the challenging tides and promising winds of San Francisco Bay.
The vessels are new for 2013 too and the crew will grapple with 22 meter catamarans that are powered by a wing sail which stands 20 meters above the deck.
The competition begins Saturday with two races -- and home hopes Oracle will want to win them both to help lift the storm clouds of controversy that have overshadowed them in the build up to this year's America's Cup.