New Zealand could clinch the Cup with a win in the second race scheduled for Wednesday, although it may not go ahead after high winds caused the race to be postponed.
The winds were considerably lighter than on Tuesday, when racing was cancelled, and New Zealand turned in a textbook performance that left Oracle with nowhere to turn. Oracle, once the favorite to retain the title that it won three years ago, still needs eight victories to hold on to the trophy.
New Zealand won the start and never trailed, crossing the finish line 15 seconds ahead of the Cup defender, although Oracle closed the gap briefly on the crucial upwind leg before losing ground again with a poor tacking maneuver.
"Every win is so hard. You're thankful for every win you get," said New Zealand skipper Dean Barker. "You have two boats that are pretty even in performance."
New Zealand dominated matches between the two teams in the first week of the America's Cup finals on San Francisco Bay, then lost momentum over the weekend when a vastly improved Oracle won its second and third matches, raising hopes of a last-minute comeback.
Oracle, which lost six of the first seven races in the series, became far more competitive after making changes to its twin-hulled AC72 and has greatly improving its upwind tacking. But Oracle's new-found speed appears most pronounced in heavier winds, and the breezes were comparatively light Wednesday at around 18 knots.
Tuesday's scheduled races were canceled after a seasonally strong out-flowing tide and high winds created conditions that exceeded safety limits set for the delicate 72-foot catamarans.
Organizers set the limits on wind speeds in the America's Cup after Swedish team Artemis Racing suffered a fatal training accident in May.
A proposal by Oracle this week to increase the wind limits for racing was rejected by New Zealand.
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 victory. On Saturday, New Zealand narrowly avoided catastrophe with a near-capsize that could have cost it the race.
But Wednesday's first race reverted to form, with New Zealand's steady performance proving more than enough for victory.
Oracle skipper Jimmy Spithill said he was hoping for more wind and was not yet prepared to let the coveted trophy go. "It's a long way from over," he said.