Blues boss Jose Mourinho has made it clear Rooney is his only transfer target this summer, but United are insistent the 27-year-old is not for sale.
"I think Chelsea have made their interest known. That's a decision for them and Wayne to come to," Lampard told Sky News.
When it was suggested to Lampard that Mourinho usually gets his way, Lampard agreed, saying: "Yes he does, I think that has shown, but when you're talking about us here we've got a big squad, we've got three or four strikers already.
"We're going into the season strong, but if the manager wants to add another player we all hope he gets his man."
Lampard is unwilling to speculate on whether Mourinho will have his wish to sign Rooney fulfilled.
"I'm really not sure. I don't know enough about it," he said. "I didn't speak to Wayne about it when I was with England last week. He was training and he was focused.
"I'm not privy to transfer stuff. That's for clubs to decide. I'm a player. I just keep my mouth shut, and train and play."
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