|Megan Rapinoe and Team USA survived the stiffest possible challenge from Canada. (Getty Images)|
Alex Morgan headed in a Heather O'Reilly cross in the 122nd minute to give the U.S. an epic 4-3 win in their Olympic semifinal against Canada.
The U.S. trailed three different times but pulled even every time to go into extra time tied at 3-3. In the second minute of injury time of the second extra time period, Morgan connected with O'Reilly's cross to send in a looping heard from 6 yards and send the U.S. to Thursday's London final.
The U.S. will face Japan at 2:30 p.m. ET.
The goal will immediately remind U.S. fans of the 122nd-minute Abby Wambach header that saved the U.S. against Brazil in last year's Women's Cup, though somehow Thursday's semifinal proved to be the even greater match.
Sinclair opened the scoring in the 22nd minute with a well-worked goal, taking a cutting pass from Melissa Tancredi and dribbling past the U.S.'s Kelly O'Hara to score unmolested from seven yards.
The U.S. answered in the 54th with an unusual goal from Megan Rapinoe, who took a corner kick directly to the near post. Canada was slow to react, and the ball squeaked in without another American touching it.
A flurry of goals between the 67th and 80th minutes left the match tied at 3 and cranked the drama to near-unbearable levels. Sinclair powered home a header from a Tancredi cross to restore Canada's one-goal lead, only for a rocket-strike from outside the box from Rapinoe to even it at 2.
Sinclair amazingly put Canada back ahead only minuites later with a perfectly-weighted header into the corner off a Canadian corner kick. But then came the most controversial moment of the game, as the Canadian goalkeeper was called for stalling, giving the U.S. a free kick inside the box. The ensuing kick hit a Canadian hand, giving the U.S. a penalty kick Wambach converted off the post.