The 19-year-old Sao Paulo winger has been the subject of reports which say United and his club have agreed a deal.
But that is not the case according to Ferguson, he spoke to reporters in a press conference in Shanghai on Monday, saying: "It's not correct. We haven't reached an agreement for the player.
"We have shown an interest, but until such time we get a deal agreed, we can't say he's our player."