Andreas Pereira scored the only goal of the game in bizarre circumstances at wintry Platt Lane.
Chances had been few and far between in the Under-18s’ friendly match, but in the 61st minute, an inexplicable lapse by City keeper Ian Lawlor allowed United to snatch the deciding goal.
Minutes earlier, the Northern Ireland youngster had made a brilliant save to deny fellow countryman Patrick McNair but, after the Reds’ next attack had broken down, the young keeper allowed the ball to slip from his grasp as he attempted to despatch the ball upfield.
The ball fell to James Weir whose snap-shot was blocked, but Pereira was on hand to snaffle up the rebound and drive the ball into the Blues’ net.
Both teams had to contend with a broad spectrum of elements which included high winds, driving rain and the occasional outbreak of bright sunshine, but stuck to the task to produce a feisty contest.
United had the better of the first half with Jack Barmby posing the biggest threat in front of goal, but even he had trouble with the direction of his shooting.
At the other end United’s young Italian keeper Pierluigi Gollini made one or two vital, if sometimes unorthodox, saves to keep the City attack at bay. The second half was much more finally balanced with both teams failing to put a finishing touch to their approach play.
Meanwhile, on an adjacent pitch United’s Under-16s were beaten 6-3 by their Manchester City counterparts.