United are taking part in the NexLions Cup in Singapore next month.
The Reds will face Sporting Lisbon in the Under-19 tournament at the Jalan Besar Stadium on 14 December.
There is a potential clash against local rivals Liverpool with the third/fourth play-off and final scheduled for Sunday 16 December after the Merseysiders tackle a Singapore Selection.
Warren Joyce will finalise his squad at a later date but Liverpool's provisional party includes the likes of Adam Morgan and Jerome Sinclair, who have appeared for the first team.
More: Under-18 fixtures | Under-21 fixtures