DURBAN, South Africa (AFP) - Manchester United manager Sir Alex Ferguson has claimed that Cristiano Ronaldo would be doing the 'worst thing' for his career if he succeeding in engineering a move from Old Trafford to Real Madrid.

The 23-year-old Portuguese forward once again refused to rule out a move to the Spanish champions over the weekend, despite Ferguson's insistence last Friday that he would not be leaving Old Trafford.

But Ferguson, in Durban ahead of United's friendly clash with Orlando Pirates on Tuesday, insisted again that Ronaldo will be staying at United.

And he also warned the player that Madrid is the last place he should be attempting to move to.

Ferguson said: "If you were asked for advice by your son, you would give him the best advice and the worst thing Ronaldo could do at the age of 23 is to go to Real Madrid.

"He is at the right club and a fantastic football club and the future is that he has signed a five-year contract and has four years left. That's definite because I have seen his signature.

"In the modern-day, young lads can be twisted by the talk of money, but if you saw Ronaldo after the Champions League final, he was the happiest boy in the world. I genuinely believe that I know what the best club in the world is for him and that is Manchester United.

"When you have young players, you want the best for them and you want to do the best for them."

United midfielder Michael Carrick has urged Ronaldo to think again about his future after insisting United are on the verge of more glory.

Carrick said: "The best thing I have done is to come here (from Spurs). For me it is a no-brainer.

"Everything that surrounds the club is moving in the right direction and we want to build on that, but we have to use what we have achieved. We drive ourselves on and we expect so much of each other.

"People from outside have nothing to do with us but we know what we are capable of and that means more European Cups and Championships."

Ferguson remains in the hunt for Spurs hitman Dimitar Berbatov, despite Tottenham's attempts to keep the Bulgarian at White Hart Lane.

But the United boss admits that adding new blood to his squad is not easy, despite last season's Champions League win.

He said: "We did a lot of stocking up last summer, buying four players of good ages as part of a policy of bringing in footballers who could develop and we think there is further progress there.

"I had 23 players in Moscow and they will still be there for this season because we are happy with the squad.

"It is difficult for us to buy and improve on that because we know why clubs don't want to sell their best players and we don't either."