The 28-year-old spent last season at Camp Nou, scoring 14 goals and providing 14 assists in 49 appearances as Barcelona won LaLiga, but the Spanish club chose not to trigger a €30m purchase option before the June 15 deadline, with the cost deemed too high after they agreed an €80m deal for Anthony Gordon from Newcastle.
Manchester United are now focused on finding a permanent buyer for Rashford this summer, with ESPN reporting that intermediaries are being invited to bring realistic proposals to the club.
The club has set a valuation of £40m, though reports indicate a release clause at that fee explicitly excludes Liverpool and Manchester City.
Rashford has not given up hope of returning to Barcelona and reportedly still views Camp Nou as his preferred destination, but United are not willing to send him back on loan and are pursuing a clean sale instead.
Arsenal and Chelsea have been made aware that United will sell Rashford to them this summer, according to reports, while Rashford himself is said to prefer staying at United and seeing out his contract rather than joining another Premier League club.
The situation has created an unusual dynamic for Rashford heading into the World Cup. He spent last season at one of Europe's leading clubs, performed well enough to earn widespread praise, and now faces the prospect of either a permanent exit from Old Trafford this summer or a return to a club where his long-term future has remained uncertain for the best part of two years.
United manager Michael Carrick has indicated he is open to reintegrating Rashford if no sale is agreed, though the club remains clear that a permanent departure is the preferred outcome.