UPDATE 1-Olympics-Soccer-U.S. grab extra-time winner to reach final

* Morgan heads winner for determined Americans

* Sinclair hat-trick not enough for Canada

* U.S. to face world champions Japan in final

(Adds quotes)

MANCHESTER, England, Aug 6 (Reuters) - Reigning Olympic

champions the United States beat Canada 4-3 thanks to an Alex

Morgan goal late in extra time to reach the women's soccer final

after an extraordinary match on Monday.

With the players on both sides exhausted, penalties looming

and the referee looking at her watch, Morgan powered home a

header to put the U.S. in front for the first time after Canada

had led three times in a pulsating game at Old Trafford.

The winner came with 122 minutes and 25 seconds on the

clock. Sixty seconds later, the match was over.

"I'm still in shock thinking of what just happened," Morgan

told reporters. "I don't care who scores as long as we score and

that's all that matters.

"I didn't even see it go in. I just try and be in the right

position.

"It was a crazy battle. Coming back and back and back. After

we scored they scored, it was amazing."

The U.S., who have now reached all five women's Olympic

finals, taking gold in 1996, 2004 and 2008, will meet Japan in

Thursday's gold medal decider at Wembley Stadium seeking their

third successive gold and their fourth in total.

Japan, who overcame France 2-1 earlier on Monday, beat the

U.S. on penalties in last year's World Cup final.

Canada's stunned players were in tears at the end and

Christine Sinclair, whose hat-trick looked as though it would

prove enough for victory, was especially distraught.

But every time she scored, the U.S. showed the mark of

champions and responded for a fifth successive win in the

tournament to claim a place in the gold medal match.

"I'm very proud of this team for making the final," said

American Abby Wambach. "I never had a doubt.

"It's exactly what we hoped for (playing Japan in the final)

after that World Cup loss."

DELIGHTFUL SLALOM

Sinclair had opened the scoring with a delightful goal after

22 minutes when she slalomed past two defenders after being set

up by Melissa Tancredi.

The U.S. equalised with a rare goal scored direct from an

inswinging corner by Megan Rapinoe that beat goalkeeper Erin

McLeod and two defenders at the near post.

Sinclair put Canada back in front after 67 minutes with a

firm header to start a wild scoring spree of four goals in 12

minutes - two from each side.

Rapinhoe equalised again three minutes later with a fierce

angled drive from the edge of the box that went in off the far

post before Sinclair got her hat-trick to put Canada 3-2 up with

another header after 73 minutes, her 143rd goal for her country.

But in the 80th minute the U.S. equalised for the third time

when Wambach scored her 143rd international goal with a penalty

after Marie-Eve Nault was harshly judged to have handled in the

area by Norwegian referee Christiana Pedersen when a freekick

struck her elbow as she was turning away from the ball.

Extra time looked set to end without a goal after Wambach's

header hit the bar in the 119th minute but that was not the last

of the drama and deep into added time Morgan headed in a

right-wing cross for the dramatic winner.

"The heart we showed today was absolutely huge," said

Rapinoe. "It's a little bit of a trademark of our team. We came

back three times today and scored four goals. We showed great

heart."

(Writing by Mike Collett; Additional reporting by Steve

Keating; Editing by Ken Ferris)