Dunfermline substitute Declan McManus came closest to giving either side a lead to take into Friday’s second-leg as both goalkeepers were forced to display their full repertoire of skills.
It was the red card shown by referee Bobby Madden to Pars defender Lee Ashcroft that was the main talking point.
There appeared cover that would have denied Scott McDonald a goalscoring opportunity had Ashcroft not bundled the striker over, but he was ordered off.
With United and Dunfermline finishing third and fourth in the Championship, they were faced with the prospect of six matches to seal the promotion they craved.
But, going into the first of them, Dunfermline’s run of ten matches without defeat ensured confidence was high despite not having beaten United since August 2011.
For the visitors, the turmoil of a season that saw them dispense with the services of manager Ray McKinnon in favour of Csaba Laszlo, in a bid to overhaul St Mirren had to be forgotten about, with the remaining chance of promotion by the back door.
In a cagey opening last night, the ball spent more time being booted from one end to the other in the air, rather than on the deck where the likes of Scott Fraser and Billy King for United, and Kallum Higginbotham and Fraser Aird for Dunfermline could make the desired impact.
It was Aird, however, who appeared most likely to create a breakthrough as the tie settled down. In the tenth minute, the former Rangers winger slung over a cross from the left that sparked minor panic in the United defence but, when the ball fell invitingly, Nicky Clark slipped at the wrong moment.
Six minutes later, Aird made a bee-line for the United box, leaving defenders trailing in his wake but his cross evaded his supporting team-mates.
One cross-field diagonal from Fraser in the 22nd minute that sent King scampering clear on the left gave Dunfermline a reminder of just what the United youngster could offer in attack.
The Pars were forced into an unwanted change in the 25th minute when striker Andy Ryan pulled up and was replaced by McManus. The substitute was instantly in the action as he appealed for a penalty for a push as he tried to reach Clark’s low centre
When McManus was felled by Bilel Mohsni 25 yards out, Aird’s free-kick that curled over the top of the crossbar was wasteful but the replacement came within a whisker of the opener seven minutes from the break. Again Aird was at the heart of it on the left as he curled in a superb cross from Higginbotham’s pass but McManus’s back-header crashed back off the bar.
With Stewart Murdoch having to deny McManus with a last-ditch tackle and James Vincent volleying over from the resulting corner, Dunfermline were building up a head of steam. But United burst into life on half-time when Fraser’s volley was deflected wide.
At the start of the second half Clark should have done better than send a tame header into the arms of Deniz Mehmet.
Mehmet was made to work harder in the 53rd minute and did brilliantly to claw Aird’s shot away from the top left-hand corner. However, just as the home side seemed to be getting on top, Ashcroft was red-carded.
United scented blood and Fraser screwed a shot just wide before a McDonald’s effort was somehow palmed round the post by Lee Robinson.
Mehmet superbly tipped Clark’s header over the bar in the 64th minute but United took a stranglehold on proceedings as time wore on and Mohsni saw a header deflected over.