Macclesfield wasted a golden opportunity to put themselves among the League Two front runners when they fluffed a succession of chances.
Though they were gifted a second-half equaliser they will be disappointed not to have converted their dominance.
After dominating the first half, skipper Tommy Widdrington allowed Jermaine Easter to evade his attentions, the tall striker, glancing home from eight yards to give Cambridge the lead.
The Cheshire side had bossed the opening stages with Danny Whitaker forcing a good save from John Ruddy with a powerful low strike.
Matthew Tipton then saw a drive from the angle fingertipped over the bar before he got in the way of a goalbound Tony Barras header to deny his side the opener.
Ashley Nicholls wasted Cambridge's best early chance has he sliced wide with men free to both his left and right. But after they scored they nearly added another immediately, John Turner gliding a curling shot inches past the post.
Macclesfield were gifted the equaliser on 49 minutes when Ruddy dropped a downward header to allow Tipton to turn neatly and slot home his fifth goal of the season from eight yards.
Easter then saw a powerful low drive deflected inches wide before lashing another chance into the advertising hoardings from close range.
Macc sub Mike Sheron then introduced some quality, setting up Tipton for a simple near post tap-in only for the striker to completely fluff his lines.
Macc should have sealed all three points at the death from only six yards out Barras unerringly picking out the keeper with a free header.