Steve Smith and Mitchell Starc have been ruled out of Australia's white-ball tour of South Africa with injuries, but are expected to be fit for the World Cup.

Cricket Australia said star batsman Smith had a tendon issue in his left wrist and must wear a splint, while pace spearhead Starc was struggling with groin soreness since returning from the Ashes series against England.

They will miss the three Twenty20s and five one-day internationals against South Africa from 30 August - 17 September.

Chief selector George Bailey said they were taking "a conservative approach" with the pair in the build-up to the ODI World Cup in India in October.

"With the World Cup the priority of the squad, it was determined on advice that it was best for Steve and Mitchell to join the group in India," Bailey said in a statement late Friday.

Australia are scheduled to play three ODIs against India before the World Cup starts.

The T20 squad was already missing heavyweights Josh Hazlewood, Cameron Green and David Warner, who are all being rested after the gruelling Ashes campaign.

Test and ODI skipper Pat Cummins is another absentee as he recovers from a fractured wrist. Cummins will join the squad for the ODI leg in South Africa but was not assured of playing, Cricket Australia said.

Ashton Turner will replace Smith for the T20s and Marnus Labuschagne for the ODIs.

Starc's absence opens the door for rapidly rising fellow left-arm quick Spencer Johnson to remain with the squad for the rest of the tour after the T20s.