Ryan Bird scored twice on his Cambridge debut but the Conference Premier title hopefuls could only draw at Dartford.
Bird's impressive brace came early and the visitors looked comfortable with their lead until an Elliot Bradbrook penalty sparked a Dartford fightback.
Max Cornhill then headed in an Alex Woodyard cross to equalise before team-mate Danny Harris's quality strike.
The U's then saw Ashley Chambers miss a penalty but Luke Berry headed in a free-kick to earn them a point.
Bradbrook's penalty came after Greg Taylor fouled Woodyard, but United's Chambers - fouled by Mathew Mitchell-King - could not find the net when Alan Julian saved his spot-kick.
VIEW FROM THE DRESSING ROOM
Dartford boss Tony Burman told BBC Radio Kent:
"I've got to give the guys a lot of credit to fight back to 2-2 before half-time. We're playing against a very, very good side but the spirit, fight and belief is back in there.
"You can't take your foot off the pedal and the set play has been the end of us in respect of winning the game.
"It was end to end. Yes, I wanted three points, but I'll settle for one."
Dartford 01 Julian 04 Sterling 14 Mitchell-King 05 Clark Booked 31 Stevenson Booked 30 Woodyard (Noble - 83' ) 10 Bradbrook 20 Burns 06 Cornhill 11 Harris 40 Wall Substitutes 19 Swallow 36 Kamara 08 Noble 24 Wellham 15 Collier Cambridge United 01 Sullivan 06 Miller 03 Taylor 04 Coulson 14 Tait 08 Champion 07 Donaldson (Berry - 70' ) 23 Chambers 25 Bird (Arnold - 52' ) 10 Elliott 17 Hughes (Gillies - 62' ) Substitutes 24 Arnold 13 Norris 02 Roberts 29 Gillies 18 Berry
Ref: Robert Whitton