(Reuters) - D.C. United scored with their only shot of the match to consolidate their league-best record with a 1-0 away win over Montreal Impact on Saturday.
A 13th-minute goal by midfielder Chris Rolfe was all United needed to post their 13th victory in 25 Major League Soccer games this season.
Montreal dominated possession and had 25 shots to United's solitary effort, but the result extended Washington's lead in the Eastern Conference to 10 points.
Columbus Crew moved into second place in the East with a come-from-behind win as Sierra Leone striker Kei Kamara scored twice in the second half in a 2-1 victory over Colorado Rapids.
In the Western Conference, Vancouver Whitecaps regained top spot when they hammered Real Salt Lake 4-0.
The Whitecaps scored twice in each half, with Uruguay midfielder Cristian Techera notching both second-half goals.
Sporting Kansas City also continued their domination over Toronto FC with a 3-1 victory. Kansas City have only lost once in their past 14 matches against Toronto.
Orlando City and Philadelphia Union drew 0-0, while in Houston the Dynamo beat the San Jose Earthquakes 2-1 with a late goal by Brazilian midfielder Alex to stay in playoff contention.
(Reporting by Andrew Both in Cary, North Carolina; Editing by Greg Stutchbury)