Leeds chairman Peter Ridsdale says he sacked David O'Leary because of his failure to take the club into the Champions League.

O'Leary was fired on Thursday amid speculation he had fallen out with Ridsdale over the proposed sale of defender Rio Ferdinand to Manchester United.

But Ridsdale insists no deal has been struck with the Old Trafford outfit yet and that O'Leary was dismissed for underachieving.

Leeds have failed to qualify for the Champions League for the past two seasons, despite an outlay of �100m on new players.

"We felt that having spent around �100m and for two years running failing to get into the Champions League it was time to make a change," Ridsdale said.

"We agreed with David at the start of this season that the Champions League was the only measure of success and we failed to achieve that.

"I understand the shock, but most Leeds supporters have told me what they want to see is silverware and after a �100m investment we have failed to achieve that.

"After four years, given some of the pressure off the field perhaps it was time to freshen up and make a change. It was fair to everyone to make a fresh start.

"It was probably the most difficult decision I have ever had to take. David and I are very good friends.

"I thought David was magnificent - he took it with dignity. What he has done is take us a long way and let's not forget that."

Ridsdale dismissed speculation he had agreed a �30m deal with Manchester United for England star Ferdinand.

"Rio Ferdinand is contracted to Leeds and I have no intention of selling him," Ridsdale said.

"He has a clause in his contract that says he can't go to another Premiership club.

"We've had no offers for him and if I've got anything to do with it he'll see out his contract.

"I'm not stupid enough to say never is never but we've told Rio we do not want to sell him and today's decision had nothing to do with Rio."

A number of managers have already been linked with the Elland Road hotseat and O'Leary claimed to know who his successor was.

But Ridsdale said a decision about a new boss had not yet been reached.

"There is no successor nominated or indeed approached and we have to decide who we believe is the best manager to take us to the next stage," he said.

"I haven't approached anybody. At the moment we have a shortlist which has been added to because a number of people have let it be know they would like to be considered.

"I've been pleasantly surprised by the interest expressed by some quality managers."