World number one Rafael Nadal [Images] will lead Spain's challenge in the Davis Cup semi-final against the United States in Madrid next week, captain Emilio Sanchez Vicario said on Tuesday.

Along with Nadal, Sanchez Vicario called up David Ferrer, Fernando Verdasco, Feliciano Lopez and Nicolas Almagro for the tie, with the latter named as cover for the four-man team in case of any setbacks during the preparations.

"It takes a while to adapt to playing at altitude and if all the players are there from the outset, we are better able to cope with any emergencies that may occur," Sanchez Vicario told a news conference.

He denied Almagro's presence was prompted by any worries that Nadal may be suffering from fatigue after he was knocked out of the US Open [Images] in the semi-finals two days ago.

"Rafa has had a spectacular season and I am delighted because he has a lot of confidence at present," Sanchez Vicario said.

"He lost a match but the tiredness and stress are within normal limits. He has a few days to recover, to sleep and relax, before he comes here. He is very enthusiastic about this tie and when he's like that there is no problem."

The semi-final against the holders will be held outdoors on clay in Madrid's 21,000-seat bullring at Las Ventas on Sept. 19-21.

"The United States are the champions, have a great team spirit, and have been together for many years," Sanchez Vicario said. "All the games will be very difficult and it should be a great spectacle."

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