Cristiano Ronaldo ended his six-game goal drought by lashing in a 51st-minute goal to set United on their way to a 2-0 win over Brighton & Hove Albion that lifted the hosts to fourth place in the Premier League.

Bruno Fernandes added the sealer in the seventh minute of stoppage time, with virtually the last kick of the game, after a rapid break as Brighton committed men forward in search of an equaliser.

United had failed to win any of their past three games despite taking the lead each time -- twice in the league, against Burnley and Southampton, and in getting eliminated from the FA Cup by second-tier Middlesbrough.

"First half was Mr. Hyde, second half Dr. Jekyll, and for a change it (the result) was different," United manager Ralf Rangnick said.

Helping United's cause against Brighton was visiting defender Lewis Dunk getting sent off three minutes after Ronaldo's goal for a professional foul, bringing down Anthony Elanga as the winger was through on goal.

Dunk was initially shown a yellow card but it turned to a red after a video review.

United moved above West Ham and into the Champions League qualification positions, four points behind third-place Chelsea but having played one game more.

Ronaldo had been on his worst scoring run in 13 years at club level but ended that by cutting inside, after teammate Scott McTominay dispossessed Yves Bissouma, and powering a shot into the far corner from the edge of the box.

The Portugal forward headed wide from Fernandes' cross later in the half, kicking the post in frustration, but his display was praised by Rangnick.

"Very important not only that he scored but it was an outstanding goal," Rangnick said.

"It was important for all of us, but his overall performance was one of the best since I arrived here."

Brighton boss Graham Potter felt it was an opportunity missed to record a first Seagulls win at Old Trafford -- after a game in which Jakub Moder went close to scoring the opener in the first half and had a second-half effort rattle the bar.

"I think the boys felt that and even at 11 v 11 I still felt we could have got back into the game," Potter said.

"OK, we've conceded a goal but I still felt it was there. But 10 v 11 makes it very, very difficult for us."

Australian Associated Press