Given that Montrose had eliminated Kilmarnock in the previous round, Stevie Campbell's lads always knew that this was going to be a far from easy tie and that was just how it panned out.
Things were not made easier through the fact that left-back Gordon Pope didn't make it after being injured in the Forfarshire Cup tie at Brechin the previous Tuesday. In addition, Chris Jeffrey was only just back from injury.
As a result, Sean Fleming stepped back to left-back and Billy Russell filled in for him in the wide left of midfield. Otherwise, the team was on the usual lines and lined up in a 4-4-2 formation - Curtis; Mulligan, McMechan, McGrath, Fleming, Andreoni, Mathieson, McCord, W Russell, Feeney, Jeffrey.
Clear-cut chances were few and far between. Home keeper Stewart McKenzie saved a Marco Andreoni header early on and Robbie Feeney stabbed a shot just wide after 27 minutes. However, in the time added on which followed Billy Russell being stretchered off with a suspected broken leg after 33 minutes, the first-half deadlock was broken.
Billy Russell's replacement, Scott Paterson, hit a high hanging cross to the far post and Feeney nodded in from point-blank range a minute from the break. It was a similar story in the second half with United still finding it hard to get the better of the Montrose back lot.
However, they did get behind the defence nine minutes after the restart and should have added a second when Philip McGrath's wayward shot turned into a good cross, but Chris Jeffrey, almost on the goal line, somehow contrived to head over.
Eleven minutes later, Scott Mathieson failed to make contact with an Andreoni cross right in front of goal, leaving United still needing the comfort of a second.
It duly arrived three minutes later when a corner was only cleared as far as Paterson and his measured volley from 22 yards took a deflection on its way into the net.
Indeed, although two ahead, United were under considerable pressure in the last quarter of the game. However, they too showed they are no slouches at defending either and keeper Matthew Curtis was never really tested as the Tannadice teenagers moved into the next round with a degree of comfort.
Team: Curtis, Mulligan, Fleming, McMechan, McGrath, Mathieson, McCord, Andreoni, Feeney, Jeffrey (J Russell 59), W Russell (Paterson 33). Subs not used; Travers, O'Byrne, Newman.