United’s unbeaten home record stretches back 14 months, to when City beat them last September, but it was not plain sailing against promoted Brighton, who proved spirited opposition in the first league meeting between the sides since 1983.
Ashley Young forced the goal in the 66th minute, his shot deflecting off defender Lewis Dunk to beat goalkeeper Matt Ryan.
Zlatan Ibrahimovic, who has not started a game since injuring his knee in the Europa League last April, came off the substitutes’ bench near the end.
“Brighton deserved more than they got,” United’s manager Jose Mourinho told Sky Sports. “They played really well and when they had the ball they were dangerous.”
United moved up to 29 points from 13 games, ahead of City’s match at Huddersfield Town on Sunday. Tottenham, however, stayed fourth on 24.
Spurs, hoping to take advantage of rivals Liverpool and Chelsea meeting each other in the late game on Saturday, dropped two points in a home 1-1 draw with managerless West Bromwich Albion.
They were behind at halftime to an early goal by Salomon Rondon and needed an equaliser from the ever-reliable Harry Kane 16 minutes from fulltime to salvage a draw.
Bottom club Crystal Palace earned only their second win of the season as a goal by Mamadou Sakho in added time beat visiting Stoke City 2-1.
A brilliant individual effort by Xherdan Shaqiri eight minutes after halftime ensured they would not keep a first clean sheet, but within three minutes new England international Ruben Loftus-Cheek, on loan from Chelsea, scored the equaliser.
Sakho’s winner, jabbing in a rebound off the post, brought Palace within three points of 17th-placed West Brom.
“That goal is worth its weight in gold,” said manager Roy Hodgson.
His team made up two points on Swansea City, who could only draw 0-0 at home to Bournemouth.
The Welsh side were upset to have a goal disallowed just before the interval when Wilfried Bony, starting in place of Tammy Abraham, found the net.
The referee decided that team mate Jordan Ayew had fouled a defender.
Watford maintained their run of having scored at least twice in every away game with a comfortable 3-0 win at Newcastle to consolidate eighth place.
Will Hughes and Andre Gray scored either side of an own goal by American DeAndre Yedlin to secure a victory that further enhanced the credentials of manager Marco Silva, who has been coveted by Everton.