Match ends, FC Halifax Town 1, Cambridge United 0.
A late penalty from Lee Gregory gave FC Halifax a slim advantage going into the second leg of their Conference Premier play-off semi-final with Cambridge.
Gregory slotted home his 31st goal of the season after Josh Coulson pushed Matty Pearson in the area.
Earlier, U's striker Sam Smith fired over from close range and Shaymen counterpart Gregory drew a fine save from Adam Smith in an even first half.
The teams meet again on Sunday for a place at Wembley.
The Shaymen reached the play-offs thanks largely to boasting the second best home record in the division.
Their only home defeat came in a 4-3 reverse to Woking in December but it was the visitors who started on the front foot.
Liam Hughes and Ryan Donaldson went close with headed efforts in the opening minutes before striker Sam Smith, making his first appearance of the season for the U's, volleyed over from six yards.
That let-off sparked the hosts into life and top scorer Gregory forced an excellent stop from visiting keeper Adam Smith with a flicked header and, from the resultant corner, Paul Marshall's volley was scrambled off the line.
The part-timers started the second half as they ended the first and Lois Maynard headed just over from an Adam Smith corner.
Thereafter the game grew scrappier and both teams turned more to long throws in deteriorating conditions.
With the match seemingly set to end goalless Coulson's silly foul on Pearson left Gregory to send Smith the wrong way from the spot.
Cambridge, for whom midfielder Luke Chadwick was quiet, will need to improve in the second leg if they are to keep alive their chances of a return to the Football League after nine years in non-league.
Cambridge United boss Richard Money told BBC Radio Cambridgeshire:
"I thought for maybe an hour - a bit longer - we were good, very good.
"There was the pressure of being pushed deeper and deeper. But they're the sort of team where you have to be in the right place all of the time. The one occasion that you're not, you get punished for it.
"It's all to play for. They've run off the pitch like they're already through. And we have to make sure Sunday is as much of a cauldron as this was here.
"This is a difficult place to come, but I thought we were worthy of coming off the pitch level."
- 7SmithBooked at 48minsSubstituted forSpencerat 73'minutes
- 5PearsonBooked at 27mins
- 20SmithSubstituted forBarnes-Homerat 90+1'minutes
- 22ChadwickSubstituted forDunkat 72'minutes
- Simon Bennett
- Shots on Target
Second Half ends, FC Halifax Town 1, Cambridge United 0.
Attempt missed. Josh Coulson (Cambridge United) right footed shot from a difficult angle on the right is too high.
Substitution, Cambridge United. Matthew Barnes-Homer replaces Sam Smith.
Foul by Lee Gregory (FC Halifax Town).
Kevin Roberts (Cambridge United) wins a free kick.
Offside, Cambridge United. Sam Smith tries a through ball, but Sam Smith is caught offside.
Attempt missed. Lois Maynard (FC Halifax Town) right footed shot from outside the box misses to the right.
Attempt missed. Matthew Pearson (FC Halifax Town) right footed shot from outside the box is too high.
Corner, FC Halifax Town.
Goal! FC Halifax Town 1, Cambridge United 0. Lee Gregory (FC Halifax Town) converts the penalty with a right footed shot to the top right corner.
Penalty conceded by Josh Coulson (Cambridge United) after a foul in the penalty area.
Penalty FC Halifax Town. Matthew Pearson draws a foul in the penalty area.
Attempt missed. Chris Smith (FC Halifax Town) header from the right side of the box misses to the right.
Foul by Kevin Roberts (Cambridge United).
Scott McManus (FC Halifax Town) wins a free kick.
Attempt missed. Scott Spencer (FC Halifax Town) right footed shot from the left side of the box misses to the right.
Attempt blocked. Matthew Pearson (FC Halifax Town) right footed shot from the right side of the box is blocked.
Substitution, FC Halifax Town. Scott Spencer replaces Adam Smith.
Substitution, Cambridge United. Harrison Dunk replaces Luke Chadwick.