Ibrahimovic was a vital part of United's success last season, scoring 28 goals in all competitions.
But the 35-year-old suffered a knee injury towards the end of the season that is expected to keep him out of action until the new year.
And with United needing a new striker on their books, they opted against offering Ibrahimovic a new contract with him unable to play for the first few months of the season.
Mourinho admitted last month the door was still open for the big Swede to make a return to Old Trafford.
And the Daily Mail claim United have already held talks with Ibrahimovic over a new contract.
It is reported Ibrahimovic is keen on re-signing under Mourinho while he has had offers from AC Milan and the MLS.
He has been continuing his rehabilitation at the club's Carrington training ground.
And there were reports earlier in the summer he could return from his injury quicker than first thought.
But United signed Romelu Lukaku in the summer for £75m from Everton meaning the Red Devils would not need to rely on Ibrahimovic as much as they did last season.
