The 36-year-old penned a new one-season deal with Jose Mourinho's side in August as he recovered from a serious knee injury, making his competitive return in mid-November.
United are not believed to require the services of the Swede for the 2018-19 campaign but according to Yahoo! Sport, he could leave Old Trafford as soon as next month.
Ibrahimovic is said to be of interest to clubs in the MLS and the Chinese Super League, whose seasons begin in March, and is expected to be presented with multiple offers for a move in the next month or two.
United, meanwhile, reportedly want to keep hold of the player until his contract expires in June but could let him leave sooner in exchange for a fee.
Ibrahimovic - last season's top scorer for United - is currently back on the sidelines with a problem relating to his previous injury.