Sir Alex Ferguson believes everything is in place for Cristiano Ronaldo to go on and become one of football's true greats.Ronaldo has already achieved plenty in his short career - appearing in the final of Euro 2004 with Portugal, lifting two Premier League titles and a Champions League trophy with Manchester United, plus a host of individual honours, including the prestigious Ballon D'Or.

On Sunday in Japan he will be part of a United side aiming to be crowned world champions by beating Ecuador's LDU Quito.

For a 23-year-old it would be a remarkable haul - with the promise of much more to come.

If Ronaldo can sustain such high performance levels, he could end up being compared to Pele and Diego Maradona - widely accepted to be the best two players of all-time.

"When you have a star like this, a young player with such huge potential, they normally make an impact very early - which is what Cristiano has done," said Ferguson.

"Pele scored in a World Cup semi-final as a 17-year-old. Maradona played for his country at 17. Cristiano was 18. All the signs are the same.

"What you don't know about him, but can say about Maradona and Pele, is that their careers lasted for a number of years.

"Pele played in two World Cup finals, as did Maradona. Maybe Portugal do not have the profile to get to World Cup finals, the same as Brazil and Argentina - so you have to judge him a different way."

It means Ferguson feels Ronaldo must maintain the high levels that brought him 42 goals last year and amass major honours in the same way Ruud Gullit and Zinedine Zidane achieved to assume the mantle of greatness. He would have to do even more to be regarded in the same company as Pele and Maradona.

Yet the Scots knows Ronaldo has all the attributes required to reach those heady heights. It is little wonder then that Real Madrid have been so keen to get him - and United just as determined the Madeira-born player should stay where he is.

"Cristiano is superb," said Ferguson.

"He has timing getting into the box, ability with two feet - and you would never associate a Portuguese winger with such magnificent ability in the air. He is like an old fashioned centre-forward.

"There are a lot of things in his favour to go on and become a legend.

"The answers will come in the next few years."

Ronaldo will almost certainly be part of a United line-up that also boasts Park Ji-Sung.

The South Korean has been guaranteed his place by Ferguson, who is promising other changes as well.

However, £30.75million record signing Dimitar Berbatov will only make the bench.

The Bulgarian has recovered from a virus, but Ferguson feels his lack of match sharpness will cost him a starting place.