Steve Smith and Mitchell Starc are dealing with injuries and have been ruled out of Australia's white-ball tour of South Africa.

Born-again allrounder Mitchell Marsh has been confirmed as captain for the ODI portion of the series in South Africa after already receiving the nod for T20 duties.

Smith is struggling with a tendon injury in his left wrist, while Starc is experiencing groin soreness following the gruelling schedule in England for the World Test Championship final and the Ashes.

Starc's issue is not related to the shoulder injury he sustained during the Ashes.

"The compacted Ashes series and the World Test Championship was a heavy load for the group, and we are taking a conservative approach to the build-up to the World Cup," chairman of selectors George Bailey said.

"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 by which time we expect them to be fully fit and available for the Indian ODI series, plus the World Cup warm-up fixture."

In Smith's absence, Marnus Labuschagne has received a reprieve, joining the squad for the 50-over games against his country of birth.

Labuschagne was left out of Australia's preliminary World Cup squad two weeks ago.

The first of three T20s against South Africa gets underway on August 31, while the five-match ODI series begins in Bloemfontein on September 7.

Australia's opening World Cup game is against hosts India in Chennai on October 8.