(Adds details on rejected proposal to increase wind limit)
By Noel Randewich
SAN FRANCISCO, Sept 17 (Reuters) - High winds on San Francisco Bay forced a postponement of 34th America's Cup sailing on Tuesday, delaying a potential final showdown between series leader Emirates Team New Zealand and defender Oracle Team USA.
A seasonally strong out-flowing tide on San Francisco Bay running against incoming wind created conditions that exceeded safety limits set for the delicate 72-foot (22-meter) catamarans, organizers said.
A proposal by Oracle to increase the wind limits for racing was rejected by New Zealand, a New Zealand spokesman said. Oracle's performance over the weekend suggests its AC72 is faster than New Zealand's in heavy winds, some observers believe.
"We requested the wind speed to be increased by 1 knot. We feel the extra knot would still keep the event safe for the teams, and it would help avoid postponements like today and allow racing to continue as scheduled," Oracle General Manager Grant Simmer said in an email.
New Zealand had been in a position to clinch the Cup and end the regatta if it could have won both of Tuesday's scheduled races. It will have another chance in two races scheduled for Wednesday, when the weather is expected to be more favorable.
Tuesday's racing was called after the boats headed out to the race course starting area near the Golden Gate Bridge, as whitecaps underneath grew frothier.
Organizers set strict limits on wind speeds in the America's Cup after Swedish team Artemis Racing suffered a fatal training accident in May. Wednesday's upper limit was 20.1 knots (23 miles per hour) for race one.
While 20-plus knot winds are not unusual on the bay and are acceptable for pleasure cruising, they are seen as too risky for the high-performance, hard-to-maneuver AC72 yachts.
New Zealand dominated racing between the two teams in the first week of the America's Cup finals but it ran into trouble over the weekend when a vastly improved Oracle won its second and third matches, interrupting the Kiwis' momentum.
Changes Oracle made to its AC72 catamaran after losing six of the first seven races in the series, combined with much-improved tacking upwind, have made the team quicker, with both crews now looking similarly polished in their maneuvers.
"We put in a lot of effort in our days off to make the changes necessary to the boat and review our crew work," Oracle grinder Shannon Falcone said on Sunday. "I feel really comfortable with where we are."
New Zealand leads the competition seven races to one, with Oracle's first two wins having been negated by a cheating penalty before the finals began. The first team to score nine points will take home the 162-year-old America's Cup trophy.
Tuesday was not the first time weather interrupted the regatta. High winds forced organizers to call off Saturday's second race while already in progress.
After New Zealand narrowly avoided catastrophe on Saturday with a near-capsize that cost it the race, Sunday's matches were among the most thrilling in yacht-racing history. The two supercharged AC72s dueled neck and neck in the second race, changing leads four times, an America's Cup record, before New Zealand eked out a 17-second victory.
"We keep a watchful eye on Oracle and we are impressed by the way they are sailing. We know we have to keep on improving," New Zealand skipper Dean Barker said after Sunday's mixed results.
Until the weekend, New Zealand had dominated the competition with superior tacking and upwind speed. New Zealand trounced challengers from Italy and Sweden to gain the right to take on defending champion Oracle in the finals.
The weekend's wild racing was a vindication for America's Cup organizers, led by software mogul Larry Ellison, whose decision to use extremely expensive and sometimes dangerous high-tech catamarans for the competition has been widely criticized.
When Ellison's team won the America's Cup in Valencia, Spain in 2010, it gained the right to set the rules and chose windy San Francisco Bay for this year's competition.
A dearth of challengers, a cheating scandal, the fatal accident in and many weeks of one-sided racing had threatened to make a mockery of the event.
The Kiwis first won the America's Cup in 1995 and successfully defended it in 2000 before losing the trophy three years later to Swiss biotechnology billionaire Ernesto Bertarelli's Alinghi in a disastrous campaign that left the team in shambles. (Editing by Alden Bentley and Eric Walsh)