Jack Barmby's goal 10 minutes from time was enough to book Manchester United's place in the final of the Premier Under-17s section of the Milk Cup.
Barmby, the son of former Tottenham and Liverpool star Nick Barmby, netted from close-range after Luke Hendry had flicked on Mats Daehli's cross.
It was his fifth goal in four games at the international youth tournament in Northern Ireland.
In the other semi-final Aspire Academy beat Desportivo Brazil 6-1.
In the Junior Section semi-finals, Everton beat Ipswich Town 5-4 on penalties after a 0-0 draw.
Their opponents in Friday's final wil be Cruz Azul of Mexico, 1-0 winners over Norwegian side Nordjaelland.