Arsenal have made an opening bid for Manchester United striker Wayne Rooney.

The Sunday Mirror says Arsenal have made a £20million bid for Rooney.

The Gunners have fired the first shots in a bidding war that is sure to spark a ­response from ­Chelsea.

Jose Mourinho has Rooney at the top of his ­Chelsea wish-list, and is ­expected to make a ­counter-bid in an effort to beat Arsene Wenger to the 27-year-old's signature.

But senior United sources last night insisted that ­Rooney is not for sale.