Sir Alex Ferguson has revealed that Arsene Wenger was "incredulous" during the negotiations surrounding the transfer of Robin van Persie last summer.

Arsenal manager Wenger wanted £25m for the Dutch striker, but much to the Frenchman's disbelief, former United boss Ferguson stood firm and insisted that he would not pay more than £22m.

"I warned Arsene we would never get to £25m. Arsene was incredulous. He could not believe that Manchester United wouldn't stretch to £25m for such a player," Ferguson wrote in his autobiography.

"I told him again: I wouldn't go to £25m. Arsene asked what my best offer would be. Answer: £22m.

"The reply was that Arsenal would take £22.5m and a further £1.5m if we won the Champions League or Premier League during the period of his contract. Deal done."

Van Persie went on to score 30 goals in all competitions last term as United won the Premier League title.