Lincoln had to be content with a point at the Abbey Stadium despite dominating the game and carving out enough chances to have secured a win that would have lifted them into the play-off places.
But it all went wrong in front of goal where they squandered three excellent opportunities in the second half.
Midfielder Mark Bailey was their inspiration as the Red Imps overpowered the home side but the one blot on his performance was a miss in the 56th minute when presented with an open goal.
Cambridge goalkeeper Shaun Marshall, trying to clear a back pass, stubbed the ball straight to Bailey 15 yards out, but he seemed so startled by the gift he sliced the shot a yard wide of the left-hand post.
There was some controversy in the 70th minute when the shaky Marshall caught a long shot from Stuart Bimson under the crossbar and then fell to the ground. However, referee David Crick waved away Lincoln claims that the ball had crossed the line.
Simon Yeo could have made up for those misses after coming on as a 62nd minute substitute, but he hit the side-netting after breaking through seven minutes after coming on and then, in stoppage time, he shot straight at Marshall.
Despite having a 41-goal strikeforce in Dave Kitson and Omer Riza, it took Cambridge 67 minutes to get their first and only real shot on target, Kitson's blaster being blocked in the box by defender Matt Bloomer.
Lincoln boss Keith Alexander said after the game: "You always have to be happy with an away point and I thought it was a magnificent performance.
"Yes we had enough chances to win it comfortably but it doesn't always happen and we will be in a very good mood to go into the crucial match at Bournemouth on Saturday." Cambridge manager John Taylor saw his team's faint hopes of the play-offs virtually disappear but said he was not too upset.
"I'm proud of what our young team have achieved this season," he said. "This was a very difficult match for us against a strong direct side but we didn't go under.
"We matched Lincoln for endeavour but we were unable to create the chances which usually goes with our game."