Barcelona - Spain's Rafael Nadal, world number one, stepped down from the Davis Cup final against Argentina later this month, due to a knee injury.

Nadal himself explained his decision Monday in Barcelona, after undergoing several medical tests.

"I did everything I could to try to get to that final. I am used to playing on court with pain and I have stood it quite well. But this is a different kind of pain, a new pain. I cannot manage to control it," the tennis player said.

He is suffering from tendinitis and will need some 15 days before he recovers sufficiently to take up normal training again. It will take him 3-6 weeks to get back to the top level of tennis, medical tests showed, after an intensive plan for recovery appeared to have failed.

Spain is set to play Argentina in the Davis Cup final November 21- 23, on an indoor carpet court in the Argentine coastal city of Mar del Plata.

Argentina seeks its first-ever "salad bowl," as the tournament trophy is known, while Spain is seeking its third title.

Nadal, 22, quit his Paris Masters quarter-final 10 days ago, when he lost 6-1 to Russian Nikolay Davydenko. He was suffering from tendinitis in his right knee.

Later, he passed on this week's Masters Cup, in an effort to concentrate on recovery towards the Davis Cup final.

"After a long and very positive year such as this, missing two very important dates for me, like the Masters Cup in Shanghai and the Davis Cup final, are very difficult times. It's clear that sometimes things happen like that and you cannot do much more," a resigned Nadal said.

He was not yet sure whether he would be travelling to Argentina to support Spain's Davis Cup team in the final, who are likely to miss the world number one on the court.

"Without me my team-mates can certainly win the final," an optimistic Nadal said. "Spain's options do not run out with me. Spain still has top-level options to be able to get the victory." (dpa)