Sanchez is spending the season on loan at Inter Milan with United paying a portion of the 31-year-old's salary.
He would be open to making the move permanent but the Italian side have reservations because of the cost of any potential deal.
Sanchez still has two years remaining on his £500,000-a-week contract at Old Trafford and is reluctant to accept reduced terms, even if it helped to facilitate a move away.
United are aware that the terms of the deal -- agreed when Sanchez arrived in January 2018 -- will make it hard to find a buyer in the summer and manager Ole Gunnar Solskjaer has been told he may have to include him in the squad for next season.
Sanchez's preference is to leave United after a disastrous spell during which he only managed just five goals in 45 appearances but accepts he may have to see out his contract, which runs until June 2022.
Sanchez joined Inter in August but injury has seen him restricted to 15 appearances in all competitions, scoring once.
If he is forced to stay at United, the former Barcelona and Arsenal star is likely to find first team opportunities even harder to come by.
Solskjaer is determined to revamp his forward line ahead of the new season, with priority placed on securing a right winger, centre forward and an attacking midfielder. Jadon Sancho, Jack Grealish, James Maddison and Harry Kane are among the names in the frame.