Eddie Johnson scored for the third straight game for DC as they registered their fourth consecutive victory in the MLS, cruising past Toronto FC 3-0 on Wednesday, while in Utah, the Red Bulls came from behind to draw 1-1 at RSL.
At DC's Robert F. Kennedy Memorial Stadium, Johnson put the hosts ahead in the eighth minute, powering a header past Toronto goalkeeper Joseph Bendik from Perry Kitchen's cross, with the 30-year-old striker notching his third goal in as many games.
Chris Rolfe doubled United's lead just before the hour mark, finishing from 10 yards after Nick DeLeon had been felled in the box by a Toronto defender.
An own goal from Toronto's Nick Hagglund in the 67th minute completed DC's victory, as they rose to 37 points, one behind Sporting at the top of the Eastern Conference with a game in hand.
RSL missed the chance to reduce Seattle Sounders' lead in the West to just three points as they were held at home by New York.
Joao Plata put RSL in front in the 19th minute, converting from just inside the area, after the Red Bulls had failed to clear the danger from an earlier attack.
But 12 minutes into the second half, Tim Cahill teed up Thierry Henry on the edge of the box and the Red Bulls skipper curled his shot into the bottom corner of the net to make it 1-1.
RSL almost took the lead in the 71st minute but Christopher Schuler's strong header from Plata's corner was blocked on the line by New York defender Ambroise Oyongo.
Eight minutes later, another visiting defender Jamison Olave clashed with fellow Colombian Olmes Garcia.
Olave appeared to squeeze Garcia's testicles, which saw the RSL forward dramatically roll around on the pitch in pain and prompting a scuffle between the two teams.
With the referee having not seen the initial incident, Garcia was then yellow-carded for simulation while Olave escaped sanction, and the Red Bulls survived the closing stages to claim a point.
The draw saw RSL move to 33 points in the Western Conference standings, second behind Seattle (38).
In other results, New England Revolution defeated Colorado Rapids 3-0 and Chicago Fire drew with Vancouver Whitecaps 0-0.
