Several British newspapers had reported that United had agreed a £26 million fee for the 19-year-old, who can play as a winger or an attacking midfielder.
Speaking during United's Asian tour, Ferguson said: "It's not correct. We haven't reached an agreement for the player. We've shown an interest but until such time as we get a deal agreed, we can't say he's our player."
United's transfer policy under the Glazer family's ownership has been criticised, with long-term target Eden Hazard joining Chelsea and Arsenal striker Robin van Persie unlikely to end up at Old Trafford despite the club's interest.
"We've signed two players in the summer: Kagawa and Powell. We think they both have fantastic potential.
"At this moment we're looking at other options in terms of bringing other players in.
"We're not lying on our backsides doing nothing. We're trying hard to bring other players to the club."