Houston Dynamo and Los Angeles Galaxy are in the box seat to advance to the MLS Cup final after both claimed convincing wins on Sunday.
Dynamo came from behind to secure a 3-1 victory over DC United in the first leg of the Eastern Conference Championship, while Galaxy thumped the Seattle Sounders 3-0 in the opening game of the Western Conference Championship.
Second-half goals from Andre Hainault, Will Bruin and Kofi Sarkodie proved the difference for Houston in front of a record crowd of 22,101 at BBVA Compass Stadium.
United forward Nicholas DeLeon handed the visitors the lead in the 27th minute, before parity was restored courtesy of Hainault on 63 minutes.
Bruin put Dynamo in front five minutes later, while Sarkodie found the net with nine minutes to go, leaving United with an uphill battle to prevail in the return leg.
In Los Angeles, Robbie Keane netted a brace as Galaxy turned on the style at the Home Depot Center.
Keane opened the scoring with a header on the stroke of half-time after Landon Donovan gathered a loose ball on the edge of the box and found the Republic of Ireland striker with a precise chip.
Mike Magee doubled the advantage in the 64th minute, before Keane sealed the result with his second three minutes later.
United play host to Houston in the second leg of their series next weekend, while Los Angeles travel to face Seattle in their return clash.