Jacques Kallis announced on Wednesday that he would retire from Test cricket at the end of the current Test against India but said he was available to play for South Africa in limited overs cricket.
In particular he stated his ambition to be part of his country's 50-overs World Cup campaign in Australia and New Zealand in 2015.
Andrew Hudson, the convener of selectors, was not immediately available for comment but a Cricket South Africa spokesman said there was nothing to be read into Kallis' non-selection for the squad announced on Friday.
"Jacques has not been part of the Twenty20 squad for some time and he has made it clear he wants to earn selection for the 50-overs World Cup."
Kallis, 38, has not played for South Africa in a Twenty20 international since the 2012 World Twenty20 in Sri Lanka, where he scored only 24 runs in three innings, although he took seven wickets in five matches, including four for 15 against Zimbabwe.
He has been a leading player in the Indian Premier League and in the statement announcing his retirement, he said winning the IPL title with the Kolkata Knight Riders in 2012 was "a special occasion".
Kallis has been an infrequent participant in South African domestic cricket in recent years but it is expected that most of the national players will play in the domestic Twenty20 competition which starts on January 5.
The preliminary squad is purely for administrative purposes and there is nothing to prevent the selectors from picking other players for the final squad.
Test captain Graeme Smith, who has not played in a Twenty20 international since 2011, and Alviro Petersen were other members of the Test squad not included in the preliminary squad.
South African squad: Faf du Plessis (captain), Kyle Abbott, Hashim Amla, Farhaan Behardien, Henry Davids, Quinton de Kock, AB de Villiers, JP Duminy, Dean Elgar, Beuran Hendricks, Imran Tahir, Colin Ingram, Rory Kleinveldt, Ryan McLaren, David Miller, Morne Morkel, Chris Morris, Justin Ontong, Wayne Parnell, Robin Peterson, Aaron Phangiso, Vernon Philander, Rilee Rossouw, Dale Steyn, Rusty Theron, Lonwabo Tsotsobe, Vaughn van Jaarsveld, Dane Vilas, Hardus Viljoen, David Wiese.