Eddie Johnson netted an 89th-minute winner to edge Seattle past Chivas USA 2-1, lifting the Sounders to second in the MLS Western Conference.
Nick LaBrocca had put the visitor ahead in the eighth minute, but Johnson equalised 20 minutes later and then headed home a second goal a minute from time.
The victory moved Seattle above Real Salt Lake, and within six points of the West-leading San Jose Earthquakes. Chivas USA remains second from bottom.
Manchester City has set its sights on winning titles on both sides of the Atlantic after announcing its entrance into Major League Soccer.