The Red Devils have been heavily linked with a host of players in recent days as the January transfer window approaches its conclusion.
Sanches has been touted as a potential target for United this month as Louis van Gaal looks to bolster his squad before the close of the transfer window on Monday.
And the Daily Mail is now reporting that the Red Devils are negotiating hard over Sanches as they look to push through a deal for the player, who is said to have a £60m release clause in his contract with the Portuguese club.
The same report says that Benfica would be willing to do business with United for around £30m plus add-ons.
United are preparing for their FA Cup trip to Derby County on Friday night as they look to return to winning ways after their 1-0 loss to Southampton last weekend.
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