Cambridge favourite Harrison Dunk was on target as they boosted their League One survival hopes with a narrow 2-1 win over Accrington, who can still mathematically avoid the drop.
Currently 22nd, United are now a point away from safety and play their game in hand over all the other teams around them on Wednesday.
Stanley’s five-year stay in League One is all but at an end as they dropped to 23rd place and are three points from safety with a poor goal difference.
Cambridge opened the scoring after 42 minutes when Jack Lankester’s corner was headed down by Michael Morrison and it fell to defender Dunk, who fired home his second goal of the campaign.
United looked more likely to add to the score with Doug Tharme clearing James Brophy’s header off the line and Lankester’s follow-up over the crossbar just after the restart.
Cambridge doubled their lead after 65 minutes when, on a counter-attack, Harvey Knibbs sent substitute George Thomas free and he raced into the area and slotted the ball into the far corner of the net.
Thomas was superbly denied a third for the hosts from point-blank range by goalkeeper Lukas Jensen soon after.
Stanley set up a grandstand finish when Morrison fouled Shaun Whalley in the area with Aaron Pressley scoring from the penalty spot via the post after 83 minutes.
However the Reds could not get another and look to be heading to League Two next season.