Skinstad (ribs) and Pretorius (muscle strain) are both currently unavailable and will only know closer to the time if they will be able to make the tournament, which gets under way in France on September 7.
White is likely to criticised for selecting just six non-white players in his squad, the same number as in 2003 and far below the number desired by the country's politicians.
But White is sure he has selected his strongest squad.
"It's an exciting mix of players, many of whom have been together since I started my career as head coach of the Springboks," he said.
"I have great confidence in these players. They will carry the flag for the nation during the tournament with pride."
White preferred JP Pietersen over Waylon Murray and Wikus van Heerden over Pedrie Wannenburg, while he also decided to take a third scrum-half - Ruan Pienaar - over a third hooker.
The team is largely made up of the Sharks and Bulls players who contested the Super 14 final this year, the Bulls contributing 11 players and the Sharks 10.
John Smit will skipper the side while veteran Os du Randt is the only survivor of the victorious 1995 team.
South Africa World Cup squad:
P Montgomery (Sharks), F Steyn (Sharks), B Habana (Bulls), A Ndungane (Bulls), JP Pietersen (Sharks), A Willemse (Lions), J Fourie (Lions), J de Villiers (Stormers), W Olivier (Bulls), B James (Sharks), A Pretorius (Lions), F du Preez (Bulls), R Januarie (Lions), R Pienaar (Sharks)
P Spies (Bulls), J Smith (Cheetahs), S Burger (Stormers), B Skinstad (Sharks), W van Heerden (Bulls), D Rossouw (Bulls), V Matfield (Bulls), B Botha (Bulls), J Muller (Sharks), A van den Berg (Sharks), J Smit (Sharks), G Botha (Bulls), O du Randt (Cheetahs), G Steenkamp (Bulls), BJ Botha (Sharks), CJ van der Linde (Cheetahs)