Matteo Mancosu scored twice as Montreal Impact beat DC United 4-2 to set up an MLS play-off semi-final with New York Red Bulls.

Impact made light of Didier Drogba's absence, scoring twice in the first half as Mancosu notched his first on the brink of half-time after Lauren Ciman's fourth-minute opener.

Mancosu bagged his second just before the hour and Ignacio Piatti's late goal ensured United's two injury-time efforts were nothing more than a consolation.

The Seattle Sounders also made it to the semi-finals as they left it late to beat Sporting Kansas City.

Extra-time looked on the cards as the game was goalless until Nelson Valdez's 88th-minute winner for the Sounders, who now meet FC Dallas.