United and Borussia Dortmund are in negotiations over a summer deal for Sancho.
And the 20-year-old winger has fuelled speculation by posting a photo with United star Rashford on Twitter.
The photo was an ad for Nike, with the caption: “If we're all on the same team, we'll never be defeated."
The Red Devils are hoping Sancho also becomes a domestic teammate of Rashford's this summer.
Reports in England on Thursday have suggested Dortmund will be willing to sell Sancho for £100m if United paid £60m up-front.
They would then need to make up the other £40m in add-ons and clauses.
If we're all on the same team, we'll never be defeated. #YouCantStopUs#TeamNike@Nikepic.twitter.com/7hgYdZ2doJ
— Jadon Sancho (@Sanchooo10) July 30, 2020