The 34-year-old midfielder tore an Achilles tendon playing for AC Milan on Sunday and Capello said he would need six months to recover, ruling him out of the month-long tournament that starts on June 11.
Whether Beckham will go to South Africa in a mentoring or advisory role Capello did not make clear, but the Italian was eager for the former Manchester United and Real Madrid player to accompany his squad.
"We have asked Beckham to come to South Africa with us," Capello told Spain's Gol Television.
"It depends on him and how his tendon injury is," the Italian added. "It's obvious he won't be able to play because we have to wait six months."
After sustaining the injury in Milan's 1-0 win over Chievo, Beckham flew to Finland for surgery before starting his rehabilitation.
Milan have said Beckham should complete his recovery in six months and the player said on Friday he would like to return to the club at some point.
He joined the Serie A side on loan stints from Los Angeles Galaxy in January this year and in 2009.
"I hope to play with you again and be part of this wonderful club" Beckham told Milan's website. "Once again thanks for your affection and good luck."
Milan's chief executive Adriano Galliani has said the England midfielder would be welcome back next season.
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