The Colorado Rapids edged the the Columbus Crew in penalties on Saturday and moved into the MLS Cup Eastern Conference final where they will face the San Jose Earthquakes.
The Rapids travelled to Columbus with a 1-0 advantage from the first leg but were headed for an aggregate defeat as they trailed 2-0 with six minutes of regular time remaining.
But a goal from U.S international Conor Casey took the game into extra time and a penalty shootout, where Colorado won 5-4 when Crew defender Brian Carroll missed his team's final kick.
The Crew's Eddie Gaven levelled the aggregate score in the 22nd minute with a close range effort following a cross from Guillermo Barros Schelotto that caused some confusion in the Colorado box.
The Crew went up 2-0 when Nigerian Emmanuel Ekpo picked out Robbie Rogers with a superb through ball and the winger showed excellent composure with his finish.
The Crew's hopes began to fade though in the 84th minute when Jamaican Omar Cummings, who had just missed a good chance, knocked in a cross which Casey stretched to steer in at the near post to force extra time.
In the Western Conference, Real Salt Lake host FC Dallas later on Saturday, trailing 2-1 from the first leg, while David Beckham and the Los Angeles Galaxy seek to defend a one goal lead at home to the Seattle Sounders.
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