United are hopeful they can land Sancho, despite Borussia Dortmund's insistence it will take a bid of around £120 million.
United believe that price tag is unrealistic in a transfer window impacted by the coronavirus pandemic and value the 20-year-old at closer to £80m.
Ole Gunnar Solskjaer is keen to sign a winger to complement his other forwards and Coman, 24, has emerged as an option if a deal for Sancho cannot be agreed.
United would be open to exploring a loan move for the France international, although there is a feeling at Old Trafford that Bayern would only consider a permanent transfer.
Coman has scored 32 goals in 158 appearances for the German giants after arriving from Juventus, initially on loan, in 2015.
Sancho remains United's top target in the next transfer window.
Sources have told ESPN that the England star would like to return to England after three years in the Bundesliga and views Old Trafford as an attractive destination.
United's bid to sign Sancho will be made easier if Solskjaer's team qualify for the Champions League.
They need a point against Leicester on Sunday to secure a top four finish and a return to the competition after a season in the Europa League.