Morecambe missed a chance to confirm League Two status for another year following their 18th draw of the season.
A share of the spoils at the Globe Arena moved them up to 21st in the table with two games remaining.
The draw sees them five points clear of second-bottom Barnet, who visit the Globe Arena on Saturday.
The Shrimps had made two changes from the side beaten at Crewe Alexandra on Saturday with Adam Campbell and Kevin Ellison replacing Andy Fleming and Garry Thompson.
They started well with Callum Lang, once again, looking their likeliest threat going forward.
He had a shot deflected behind inside two minutes and, from the resulting corner, Cambridge failed to clear with Sam Lavelle ultimately heading over.
Seven minutes later and Lang threatened again; this time, he collected Campbell’s through ball but was denied by keeper Dimitar Mitov.
Morecambe’s start was as bright as the visitors’ fluorescent kit but Cambridge began to get a foothold in the game after changing their shape to match the Shrimps’ five-man midfield.
They were also neater in possession than Morecambe, albeit without posing much in the way of a threat to the home side.
George Maris had their only effort of the first half, a first-time effort from 20 yards that was comfortably held by Barry Roche.
Lang saw another shot go off target and a Campbell free-kick was cleared with Steve Old well placed as the first half came to a conclusion.
Morecambe raised their tempo after the break with Lang still their likeliest source of a goal.
The second half was barely a minute old when Campbell released Lang into the area for a corner which came to nothing.
With one goal increasingly looking like deciding the match, Cambridge won three consecutive corners after Jevani Brown’s shot was deflected narrowly wide.
The last of those saw Uche Ikpeazu turn and shoot wide of Roche’s left-hand post as proceedings became increasingly tense.
Ellison could have calmed the home fans’ nerves but made a mess of Campbell’s cross when six yards out.
Maris curled another long-range attempt off target and Mitov parried Aaron McGowan’s shot with the loose ball falling to a Cambridge defender.
An increasingly open game saw Lang head off target, though Jake Carroll also shot wide for Cambridge and Alex Kenyon headed off the line as honours ended even.
Morecambe: Roche, McGowan, Lavelle, Old, Conlan, Kenyon, Rose, Campbell (Wylde 76), Lang, Ellison, McGurk. Subs not used: Nizic, Fleming, Oliver, Wildig, Lund, Muller.
Cambridge United: Mitov, Halliday, Taylor, Taft, Carroll, Amoo (Waters 76), Deegan, Maris, Dunk, Amoo, Brown. Subs not used: Iron, Legge, Elito, Lewis.
Referee: Ross Joyce.