Poland striker Lewandowski has been linked with a big-money move away from Borussia Dortmund in the summer after catching the eye of many clubs with his performances in the Bundesliga over the past couple of seasons.
Bayern are thought to be the frontrunners but there is also understood to be interest from the Premier League and United have been monitoring his situation.
Ferguson is already blessed with attacking options at Old Trafford and says it would be difficult to fit another centre-forward into his squad.
However, he is not ruling out a major summer signing and insists much will depend on whether the Red Devils land the Premier League title.
Ferguson said: "Big signings? You are normally talking about forwards but it's complicated enough as it is with the forwards I've got."
On his interest in Lewandowski, he added: "Yeah, but Bayern Munich are strong with that too.
"We just have to wait and see where we are in terms of if we win the league. Then it may be different."