Sancho, who has a contract until 2026, returned to Dortmund on a six-month loan in January. He made his name at Dortmund before a big-money move to the Premier League in 2021.

The England international has had a difficult time at United and had only played three matches off the bench after falling out with manager Erik ten Hag earlier in the season.

After a slow start, Sancho has impressed in recent weeks and was outstanding in Dortmund's 1-0 Champions League semi-final first-leg win over Paris Saint-Germain on Wednesday.

Speaking with German news outlet Welt, Kehl said Sancho had "found his smile again here".

"(United) will have seen how well he's playing. Maybe they have their own ideas or want to sell him for a profit.

"Maybe he will also return to Manchester. These things could all happen in the future."

United paid a reported €85 million (£73 million) to sign Sancho from Dortmund in 2021 but the German club has said they would not be able to afford a similar fee.

Dortmund play at Paris Saint-Germain on Tuesday and can qualify for the Champions League final with a win or a draw.