Noah Berger/AFP
The Americans, who were docked two points for pre-regatta violations before their series against the Kiwis even began, were trailing 8-1 last Wednesday and appeared destined for a humiliating defeat in yachting's most prestigious and well-known race.
But the US squad dug deep and launched the longest winning streak in the event's illustrious 162-year history, overseen by the introduction of Britain's multiple Olympic sailing gold medallist Ben Ainslie as team tactician.
On Tuesday, the Americans levelled the score at 8-8 in the best-of-17 race, finishing 54 seconds ahead of their Kiwi challengers despite being last across the start line in San Francisco Bay.
The teams, competing in AC72 catamarans capable of speeds of more than 40 knots (75 kilometres/46 miles per hour) on their L-shaped hydrofoils, go head-to-head again on Wednesday at 1:15 pm local time (2015 GMT), with a single victory for either side guaranteeing overall victory.
The US team's skipper Jimmy Spithill sensed his crew had the momentum to win regatta and praised their efforts.
"You can get wobbly in the knees or look straight down the barrel and smile; and that is what this team has done. We have come back from a very deep hole and we want this. We will come out ready to fight tomorrow," he said after Tuesday's race.
New Zealand skipper Dean Barker called the Americans' comeback "amazing", adding: "Both teams are equally hungry to win this thing.
"We got beaten today (Wednesday) and that is tough to handle, but sometimes you just have to accept those. It is frustrating, but we know we can still win this."
Only three times before in Cup history have boats won five races in a row, but those were in best-of-nine regattas where none had a chance to stretch the streak as long as Oracle Team USA has this month.
A US win would cap a remarkable comeback that ranks alongside the greatest in sporting history.
Much of Oracle's success has been attributed to 36-year-old Ainslie, who won gold at the last four Olympics in the Finn and Laser classes and who is an 11-time world champion in the sport.
Observers say his appointment on September 12, the day of the sixth regatta, could go down in the annals of the event, with his improved communication and tactics helping Oracle's stunning turnaround.
In Tuesday's second race, the Kiwis grabbed the inside lane at the first gate, forcing the Americans into a slow, wide turn and grabbing the advantage.
New Zealand fended off efforts by the Americans to close the gap in the second leg and held onto a lead of slightly more than 100 meters into the critical upwind third leg.
Oracle turned to match New Zealand's line and seemed to rocket ahead of the Kiwis. The Americans turned ahead of New Zealand and snatched a lead that only grew.
The Kiwis drew a pair of penalties at the start of the day's first race, crowding the Americans as they fiercely vied for positions.
The USA got a head start and rounded the first mark well ahead of the Kiwis.
The Americans blazed along the second leg, with speeds topping 80 kph, and rounded the second gate 29 seconds ahead of the Kiwis.
New Zealand pressed hard on the tail of the American team, which maneuvered to block opportunities to pass.
The Kiwis narrowed the gap through the critical upwind leg, as both catamarans also sailed against the tide, but the Americans held on to cross the finish 27 seconds ahead of New Zealand.
"We absolutely do believe we can win," Barker said of the winner-takes-all showdown Wednesday.
"It is one thing talking about it; we have to get everything together to make it happen."