The England captain was a major doubt after breaking a bone in his foot during Manchester United's Champions League quarter-final win over Deportivo La Coruna last month.
But his Manchester United manager insists the 27-year-old midfielder will be ready to lead his country in Korea and Japan this summer after an X-ray revealed his foot is healing well.
"The scan has shown up he is quite all right there," said the Old Trafford chief.
"He is 100% certain to play in the World Cup."
Ferguson added: "The fracture has not fully healed at the moment, but I would think in 10 days' time it should be healed.
"Then we will start a rehabilitation programme which will enable him to meet up with England in Dubai.
"He should be ready, although I'm not saying he should be ready for the first game, but he should be ready for some part of the World Cup."
Beckham was expected to be ruled out for between six and eight weeks after suffering the injury on 9 April.