Cliftonville enjoy a one-point lead at the top of the Irish Premiership thanks to this win over Ballymena at Solitude.
Martin Donnelly scored with a slightly deflected low left-foot shot in the 41st minute after Liam Boyce backheeled the ball into his path.
Dwayne Nelson made a fine save from George McMullan but Boyce netted the second with a close-range header on 71.
Gary Thompson grabbed a consolation goal for the visitors with a rising right-foot shot deep into added time.
Both teams had chances early in the game, with Barry Holland and Ryan Catney going close for the Reds and Jamie Davidson and Alan Teggart out of luck for United.
Ballymena's 17-game unbeaten run in all competitions came to an end with this defeat and the Sky Blues now drop to fifth in the league, having conceded their first league goals of the campaign.