VIDEO Of US 4-3 Canada (AET): Highlights; Alex Morgan The Hero To Send The US Into Gold Medal Match [Olympic Women's Soccer]

The ending was only befitting after an incredible roller-coaster match between these two rivals who have met so many times over the years. Canada, for so long on the receiving end of defeats to their near-neighbor, thought this might finally be their day as they took the lead three times courtesy of an outstanding hat-trick from Christine Sinclair.

It would not be enough, though, as the U.S. kept responding in a breathless second half. First Megan Rapinoe answered Sinclair's first-half strike with a goal direct form a corner, before repeating the trick with a fine strike minutes after Canada had retaken the lead. After Sinclair put her side back in front after 73 minutes, Abby Wambach equalized once more from the penalty spot. The U.S. kept pushing forward in extra time, and, just as everyone was preparing for penalties, Morgan forever imprinted herself in the storied history of U.S. women's soccer.

The match began in a tightly contested manner befitting the rivalry that has built up between the international neighbors over the years. But, while the U.S. had a couple of efforts from distance by Carli Lloyd and Megan Rapinoe, Canada was holding its own.

Going forward Canada was causing problems too. It was clear that John Herdman had set up his side with a clear tactic of testing the U.S. defense with forward Jonelle Filigno's pace in-behind. Not only was the ploy a threat unto itself, but it also allowed space between the lines for Melissa Tancredi and captain Christine Sinclair.

It was just that space that allowed Canada to take a surprise lead midway through the first period. Marie-Eve Nault was given far too much room with which to move into down the left before playing it into Tancredi, who controlled neatly before laying it off to Sinclair. From there, the experienced goal-scorer showed all her nous as she burst onto the ball before cleverly stepping inside the challenge of Kelley O'Hara and then calmly slotting the ball back across Hope Solo.

It was the first goal Solo had conceded in 368 minutes, and the U.S. looked shell-shocked at falling behind for the first time since their opening game against France.

Still struggling to control the game as it would have liked, the U.S. managed to force two presentable chances before half-time.

Morgan was at the heart of both as first she flicked a deft header wide of the post from a free-kick before setting up Wambach brilliantly, who put her own header wide of the target when well-placed in the area.

The U.S. had started the second half with increased purpose that demonstrated the full of extent of its desire to extend its record of making it to every Olympic gold medal match.

It took less than 10 minutes to get that reward, with a most unusual goal. From a corner on the left, Rapinoe whipped the ball into the near post toward Rachel Buehler, and, with two Canadian players trying to battle off the U.S. defender, the ball traveled all the way through before going in off the legs of goalkeeper Erin McLeod.

That was to prove merely the beginning of a second half of incredible drama. With the U.S. looking strong favorites to go on and book its place in the final, Canada produced a startling response.

In the 67th minute, Tancredi received the ball down the left, cut the ball back onto her right foot and came up with a perfect cross for Sinclair to rise and produce a peerless header to beat Solo for the second time in the contest.

Already having come back from 2-0 down against France, the U.S. again showed its resilience with a second equalizer just three minutes after going behind.

While there had been an element of fortune about Rapinoe's first goal, there could be no such judgement about her second. O'Hara drove a fine ball from left to right to find Rapinoe on the edge of the box, who took advantage of her yard of space to drive a stunning effort into the far corner past McLeod.

Yet, every time it appeared that the U.S. would be able to assert its dominance, Canada and Sinclair came right back. The 29-year-old once again showed her ability in the air as she rose highest in a crowded penalty area to head a corner past Solo. Her reaction spoke volumes for her own and her team's steely determination to finally put one over their rivals.

But, not for the first time, that joy would be short lived. McLeod, looking to waste away some precious seconds, paid dearly as she was penalized for hanging onto the ball for too long. From the resulting indirect free-kick, Rapinoe blasted the ball toward the goal before it was blocked by the arm of Nault. Wambach did not disappoint from the penalty spot as she slotted the ball low to McLeod's right to bring the U.S. level for the third time.

Having continued her record of scoring in every match of the competition, the veteran striker would miss a chance to further cement her hero status five minutes from the end. Morgan scampered down the left, hurdling a challenge in the box and sliding the ball invitingly across goal where Wambach slid in at the back post but could only send the ball wide of the near post.

While the U.S. was now pushing forward incessantly, Canada had its own opportunity to win it later on in regulation time as Sophie Schmidt forced a good save from Solo at her near post.

Tired legs were increasingly showing on both sides as the match went into extra time. The U.S. was in the ascendancy, though, as it continued to threaten from wide. The match could have been settled earlier as Morgan put a ball onto the head of Wambach, who looped a header that McLeod seemingly just got the faintest of touches on to help the ball onto the cross bar.

Then came Morgan's dramatic late intervention as she strained every sinew of her tiring body to put a header past McLeod from Heather O'Reilly's cross.

Canadá 3-4 USA [Semis JJOO] by Emenderk