FORT LAUDERDALE, Fla. (AP) -- Diego Serna's goal two minutes into the second half broke a 1-1 tie and helped the Miami Fusion beat D.C. United 3-1 in an MLS match Saturday night.

Roy Lassiter secured Miami's victory with a goal in the 90th minute as the Fusion broke United's season-best two-game winning streak, almost certainly eliminating the three-time league champions from reaching the playoffs.

United would probably have to win its final six games to have any hope of reaching the playoffs and earning the right to defend last year's MLS Cup title.

Serna's game-winner and eighth goal of the season was set up when Martin Machon headed a one-bounce pass to an open Serna, who headed in a shot over D.C. goalkeeper Mark Simpson.

United almost tied the match in the 62nd minute, but Bobby Convey's shot, which looked like it was headed into the upper left-hand corner of Miami's goal, got blocked by Fusion goalkeeper Nick Rimando's diving deflection.

Lassiter, who entered the match at the 82nd minute, kicked in an uncontested shot just outside the 6-yard box after receiving a crossing pass from Jay Heaps.

The victory improved Miami's record to 8-11-5 and 29 points, third in the MLS Eastern Division

Defending league champion United is 6-14-6 with 24 points, fourth in the East.

Miami scored first on Jim Rooney's goal at the 20th minute. Jay Heaps sent Rooney a crossing pass from the right wing and Rooney kicked in a shot from 8 yards which beat Simpson.

Despite the Fusion's early goal, United controlled play for most of the first half and finally came through at the 33rd minute on Jaime Moreno's 12th goal of the season.

Carey Talley's pass from 10 yards inside the midfield stripe found Moreno inside the 6-yard box, where he headed in a shot past Rimando.