The 25-year-old has been a hit for United since returning after six months out with a broken ankle.
Barcelona, Real Madrid, Inter Milan and AC Milan are reportedly among the clubs keeping tabs on the former Wigan star.
A United insider told The Sun: “Valencia has been brilliant since coming back from his injury and United want to get him sorted with a new contract.
“But there are lots of other clubs showing interest and he knows he’s in a healthy position.”
