U's defeated 1-0 at The ShayCAMBRIDGE United lost 1-0 at Halifax in the first leg of the play-off semi-final.
The U's came close early on, Ryan Donaldson headed over from a corner on 3 minutes, then forced Glennon into a good save down to his right.
Sam Smith came closest for United on 18 minutes, Tom Elliott's flick on found Smith three yards out, he fired just over the bar.
Lee Gregory was prevented from giving Halifax the lead on 28 minutes, Adam Smith tipping his glancing header over the bar from ten yards out. A minute later, Paul Marshall's fierce strike forced Smith into another fine save, before Lois Maynard fired wide for the hosts from 18 yards.
HT: Halifax 0-0 U's
The hosts came close to taking the lead on 50 minutes, Lois Maynard heading inches over Adam Smith's bar from a dangerous corner.
Liam Hughes had the first chance of the second-half for United, he broke free down the centre and forced Matt Glennon into a decent save.
As the rain came down at The Shay, both sides struggled to create any clear-cut chances. In the 81st minute, Josh Coulson was penalised for a foul on Matthew Pearson in the box and Lee Gregory calmly slotted home from the spot to put the hosts 1-0 up.
The U's couldn't find an equaliser and will have to overcome a one goal deficit in the second leg on Sunday at the R Costings Abbey Stadium.
FT: Halifax 1-0 U's
TEAM: A Smith, Roberts, Miller, Coulson, Taylor, Champion, Chadwick (Dunk, 71), Hughes, Donaldson, S Smith (Barnes-Homer, 90), Elliott
NOT USED: Bonner, Berry, Cunnington