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.

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.

"If I'm only 40 per cent, I won't go," he told Spanish radio last week. "I have to see how the knee pulls up."

Nadal was desperate not to miss the Davis date.

"Who doesn't want to play the Davis Cup final? It's my last major objective this season," he said. (dpa)