The Atletico Madrid striker has enjoyed another fine season in the Spanish capital and is one of Jose Mourinho’s number one transfer targets this coming offseason.
The Frenchman has indicated he would be willing to stay with the Rojiblancos for another season but an £84million release clause in his current contract a transfer away cannot be ruled out.
And Eric Olhats, one of those who discovered the 26-year-old, says five of Europe’s biggest clubs, including United, are keen.
"We're at the stage of gathering information from clubs who have a concrete interest," he told French television show Telefoot.
"There is an unavoidable €100m clause so that restricts the number of candidates. You have United, City, Chelsea, Barcelona and Real Madrid.
"United were the first to come and see us and the most concrete in their wishes."
United are keen to bolster their attacking options in the summer with Bayern Munich’s Robert Lewandowksi, Monaco’s Kylian Mbappe and Moussa Dembele of Celtic all being considered.