A second half goal from Simon Johnson after an earlier Frannie Collin penalty miss gave United a 1-0 win at Barton Rovers in second round qualifying.
It was United's third away win and clean sheet in the FA Cup this season and they are now two more victories away from joining the Football League clubs in the first round proper.
United manager Darren Hare gave a first start to young academy player Tom Climpson and Jack Harris was also in the 11 which began the match as he continues his recovery from injury.
Ryman Football League Division One South side United are unbeaten in all competitions so far this season, but a close contest was expected against a Barton side which plays in the equivalent-standing Evo-Stik Southern Football League Division One Central.
After a fairly quiet opening quarter in Bedfordshire, Collin put a decent opportunity over the crossbar and Sam Cruttwell brought a good save out of the home goalkeeper from a free kick.
Richard Davies made a goal-line clearance and the hosts headed just wide during a decent spell for Barton, while Collin and Cruttwell had efforts saved at the other end shortly before the break.
Harry Stannard had a goal disallowed for offside after he tucked away a Davies cross and Collin then hit the post from a free kick out wide as United made a strong start to the second period.
United then had a golden opportunity to take the lead when they were awarded a penalty only for Collin, who had scored in three of the previous four games, to miss the target.
Away goalkeeper Lenny Pidgeley pulled off a brilliant double save before United grabbed the winner in the 74th minute. Johnson headed in the rebound for his first goal of the season after Matt Bodkin's initial effort struck the crossbar.
Barton blazed a decent opportunity over the top and although it became backs-to-the-wall stuff during the closing stages, United held on to secure the win and a place in Monday lunchtime's draw for third round qualifying.
The next stage, incidentally, will take place on Saturday October 1 so United's scheduled league game at home to Horsham will be put back to a later date.
United's scheduled league fixture at home to Faversham Town this coming Tuesday will also be played at a later date because Faversham will have an FA Cup replay away to Hitchin Town after a 2-2 draw this afternoon.
United: Pidgeley, Climpson (Foster), Rowe, Davies, Butler, Stannard (Temba), Johnson (Pritchard), Cruttwell, Bodkin, Collin, Harris.
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