The 25-year-old scored 33 goals last season as the Posh won automatic promotion to League One, since when the former Grays Athletic striker has been the subject of two failed bids from Wolves for his services.
Peterborough chairman Darragh MacAnthony said: "I offered Aaron the most lucrative contract in the history of Peterborough United and Aaron has responded by putting in a transfer request this morning.
"We've therefore reluctantly placed Aaron McLean on the transfer list and, as stated before, any interested parties will have to pay the club £3million up front plus various add-ons and a sell-out clause for the transfer of his registration.
"As far as I'm concerned, if we don't get the asking price then Aaron will work out the remainder of his Peterborough United contract until 2011."