Sir Alex Ferguson believes the clash between Cristiano Ronaldo and Kaka in Manchester United's UEFA Champions League semi-final clash with AC Milan on Tuesday will showcase the two best players in the world.

The Manchester United manager has singled out the Brazilian playmaker as the Serie A outfit's key player ahead of the Premiership leaders' bid to maintain their challenge for honours on three fronts. And the Scot believes Ronaldo's displays this season have justified claims the Portugese winger is currently the game's number one talent.

Ferguson, though, has warned his side cannot afford to focus their efforts solely on halting Kaka if they are to retain hopes of claiming a second successive Italian scalp following the emphatic 8-3 aggregate win over Roma. United lost to Carlo Ancelotti's side at the quarter-final stage two seasons ago, but Ferguson is convinced his side has improved immeasurably since then.

"I wouldn't disagree with people who say Ronaldo and Kaka are currently the best two players in the world," he said. "But Milan have a lot of good other players too. Paolo Maldini is great and Clarence Seedorf has won the Champions League three times with three different teams.

"They have fantastic experience in their team. But I think we'll be better than the last time we played them and hopefully they won't be as good.

"We did create chances in our last games against them - there's no question about that. And we'll create chances on Tuesday again. The vital question is: can we take them? At that level if you don't take them then you only have yourselves to blame."

Greater challenge
Ferguson believes the maturing Ronaldo is one of the reasons his side presents a much bigger goal threat this season than two years ago, despite the fact the United attack was then led by the prolific Ruud van Nistelrooij, who left for Real Madrid last summer after scoring 150 goals for the club.

"The speed we're playing at and the penetration is creating chances," he said. "Lots of players are chipping in with their share. Ronaldo has 21 and Wayne Rooney has 20, Louis Saha 13 and Ole GUnnar Solskjaer 11. That's quite good. We have 19 different goalscorers this season. That's very high."

United's 7-1 second leg victory over Roma established the Old Trafford club as favourites to win the competition, but Ferguson knows that Milan will present a much tougher challenge. "Our tactics will be different from the Roma game," he added. "In the last game two years ago the thing that impressed me about AC Milan there was great professionalism in both games.

"There was no diving about and they played the game properly. They've been in ten finals. It's a fantastic record and they have a great history."