Dunfermline warmed up for Tuesday's Scottish Cup semi-final replay with Inverness Caledonian with a merited draw.
The Fife side rested eight first-team players with the cup tie in mind but a first-half goal from Greg Shields gave them the lead until United hit back in the second half.
United threatened first when Dave McCracken sent a header just a yard too high from a Mark Wilson free-kick but the home side hit back immediately.
Craig Wilson wasted a great chance when Billy Mehmet sent him clear but he directed his shot straight at Paul Gallagher.
But not much more was seen of Dunfermline until the final minute of the first half. It was United who made all the running and Craig Easton shot wide from 15 yards after 26 minutes when the ball broke to him in the box and he should have done much better.
Andy McLaren then carved out a shooting opportunity for himself from 30 yards but Marco Ruitenbeek did well to slap the ball over the top.
Dunfermline snatched the lead against the run of play on the stroke of half-time. Shields started the move from deep inside his own half and when Gary Mason's final cross came over, the full back managed to get on the end of it to drill a 16-yard shot past Gallagher.
United hit back in the second half but Dunfermline defended well with Andy Tod holding them together.
But the equaliser arrived on 64 minutes when Chris Innes headed a Barry Robson corner back across goal and it broke off McCracken to find the net.
The Tangerines pressed for the winner but Ruitenbeek, making his farewell appearance, made fine saves to deny Collin Samuel and Jason Scotland.
Shields also had a chance at the other end but miscontrolled the ball at the crucial time.