Athletic Bilbao president Josu Urrutia insists that the club will not allow Javi Martinez to leave for anything less than the €40mn (£32mn) fee in his release clause.

Martinez, who can operate as a holding midfielder or a centre-back, has been linked to several European giants, including Manchester United, Manchester City, Arsenal, Barcelona and Bayern Munich but the Bilbao chief has made it clear that the player will not be sold cheaply.

"If someone wants to take Javi Martinez, they will have to pay what the release clause in his contract says. For a player to leave Athletic, he must first come to us and say that he wants to go. Then, a club must match his release clause. If a club is willing to pay, but the player wants to stay, then he will stay. We are not a selling club," quoted Urrutia as saying.

Martinez is currently on national duty with the Spain at Euro 2012. His agent had recently dismissed rumours that the player and Bilbao agreed on a deal with Bayern and the 23-year-old will soon complete a move to Munich.

Meanwhile, United have stepped up their interest in FC Porto winger James Rodriguez, according to the Daily Mail.

The Colombian scored 13 goals from 20 league appearances last season and had recently signed a new five year contract with the Portuguese club, with a release clause believed to be around £40mn.

The report says that Sir Alex Ferguson is determined to land the 20-year-old and a £30mn bid from the Red Devils has already been rejected by Porto, who are determined to hold out till a club meets the player's release clause.

United have been strongly linked with Rodriguez after doubts rose over Nani's future at Old Trafford and the report claims that Ferguson now wants to sign the youngster, regardless of whether the Portugal winger stays at Old Trafford or not. The Scot would look for a player-plus-cash deal, with midfielder Anderson going in the other direction, but Porto are understood to be not so keen to welcome back the Brazilian, who left the club five years ago.