Pompey Academy conceded a late penalty as they began 2019 with a 1-1 draw against Oxford at Copnor Road.
They took the lead just before the break when a cross-shot from Stan Bridgman beat the keeper and flew into the net.
But the visitors pushed forward in the second half and were awarded a late penalty following a foul in the box.
Fabio Lopes stepped up to take it and beat Leon Pitman to secure the draw that United needed to claim the Youth Alliance South-West League title.
"We played really well as a group and thoroughly deserved to get something from the game."
Academy head of coaching Shaun North said: “We played really well as a group and thoroughly deserved to get something from the game.
“We battled well and almost got the victory, but it was an extremely competitive contest throughout.
“Oxford are a physical side and we were giving away a lot in terms of age, so I was pleased with how our lads performed.”
Pompey: Pitman; Bruce, Robb, Rew, Kelly (Kerton 71); Whiting, Bridgman; Kavanagh, Johnston (Bell 85), Teggart (Brook 64); Stanley (Lee 84)