United will announce their list of retained players at 9am BST on Friday, with Ibrahimovic the only first-team fixture whose contract is due for renewal.
According to the Daily Telegraph, talks are already underway for United to sign the Spain worldwide as Ibrahimovic's departure should be all but confirmed tomorrow with his name to be left off a list of players retained by the club.
Ibrahimovic's agent Mino Raiola said last month he did now know if his client would be back at United as he looks to resume his career after he recovers from injury.
He scored 28 goals in total for Jose Mourinho's men, including Wembley strikes as they won the Community Shield and EFL Cup.
The 35-year-old suffered knee ligament damage in the Europa League quarter-final with Anderlecht on April 20 that required surgery in May in the US.
Although there is no rule restricting a club from approaching a player excluded from their retained list at a later point regarding a new deal, the list will include details of any offers already made.
A host of big name attacking players have been linked with United in recent months to help replace Ibrahimovic and fellow forward Wayne Rooney, who could also be on his way out this summer.
Reported target Romelu Lukaku appears close to leaving Everton for former club Chelsea, while Torino striker Andrea Belotti and Real Madrid's Alvaro Morata are other options.