Onana retired from international duty in December after leaving midway through the World Cup campaign following a disagreement with head coach Rigobert Song.
He has agreed to return for the AFCON qualifier against Burundi on Sept. 12 after an intervention initiated by the Cameroon government, but sources have told ESPN that he has not yet committed to playing at the tournament -- which begins in Ivory Coast in January -- even if the Indomitable Lions qualify.
It's a boost for Manchester United, who face losing their first-choice goalkeeper for up to a month if Onana decides to play.
AFCON starts on Jan. 13 with the final scheduled for Feb. 11, a spell during which United have Premier League games against Tottenham, Wolves, West Ham and Aston Villa.
Sources have told ESPN that Onana and his representatives informed United of his decision to play against Burundi during a meeting at Carrington on Saturday.
The club were told during negotiations to sign the 27-year-old from Inter in the summer that he had retired from internationals, but sources have told ESPN that Ten Hag is sympathetic towards his reasons for believing he has to play against Burundi.
Meanwhile, sources have told ESPN that Phil Jones has been back at United observing academy training sessions.
Jones left the club at the end of last season following the expiry of his contract. The 31-year-old former England defender is still weighing up his options and has not ruled out continuing his playing career if he can get back to full fitness and the right opportunity arises.