Walaa Eldin Musa scored the only goal of the game as Sudan beat Mauritania in their second African Nations Championship match, eliminating the Mourabitounes in the process.
The defeat also signals the end of the road for Guinea, who were defeated 3-1 by Morocco in the day's earlier kick off, with Sudan now set to face hosts Morocco in Casablanca on Sunday to decide top spot.
After two matches, both Morocco and Sudan have six points, with Mauritania and Guinea, both pointless, set to contest the group's wooden spoon in their final clash in Marrakech.
Mauritania, more able to express themselves against Sudan after being outclassed during the second half of their opener against Morocco, enjoyed the first big chance of the game in the 11th minute when Bagili Babacar was thwarted by goalkeeper Akram.
The stopper kept the scores level less than 10 minutes later when Mauritania, showing the adventure that was absent against the Atlas Lions, pushed forward and almost opened the scoring as Babacar attempted to reach an errant backpass.
Sudan broke the deadlock in the 30th minute when Mohamed Tahir played a delightful ball between the Mauritania centre-backs to unleash Walaa Eldin, whose right-footed effort from close range was deflected over the sprawling Souleimane Brahim.
Mauritania introduced Karamokho Traore after the break in search of an equaliser, although it was the frustrating Babacar who went closest, when he was crowded out by Omer.