Mitchell Marsh was named Australia's new Twenty20 captain Monday for their tour of South Africa, as selectors revealed Test and one-day skipper Pat Cummins has a fractured wrist but should be fit for the World Cup.

Marsh will take the armband for the first three T20 matches since Aaron Finch's retirement, leading a squad missing Mitchell Starc, Josh Hazlewood, Cameron Green and David Warner, who are all being rested.

Cummins will also be absent as he recovers from the injury sustained in the final Ashes Test in London.

All of them will join up for the one-day leg of the South African tour.

"He has an undisplaced fracture of his left radius which requires six weeks rehabilitation," chairman of selectors George Bailey said of Cummins.

"We expect him to join the squad during the South African ODI series. We view a period of enforced rest for Pat as a positive ahead of this important World Cup campaign.

"There are still a number of games he could play before the World Cup which is more than enough for him to have a strong preparation," he added.

Rising all-rounder Spencer Johnson, power-hitter Matthew Short and left-arm seamer Aaron Hardie all earned maiden national call-ups for the T20 games.

Jason Behrendorff also returns to national colours for the first time since the 2022 Pakistan tour.

"Mitch has long been a senior player within the white-ball structure, with this an opportunity for him to add to his leadership skills at international level," said Bailey of Marsh's elevation.

"We look forward to him taking that step in South Africa."

Marsh was named as skipper for the South Africa series only, with Cricket Australia yet to commit to a full-time replacement for Finch, who played his final international last October.

An initial 18-man squad for the 2023 World Cup and preceding five-match one-day series against South Africa was also named, largely a continuation of the group which defeated India 2-1 in March.

But Marnus Labuschagne was a glaring omission, with Hardie and promising young spinner Tanveer Sangha included.

"This side has been extremely impressive for several years in limited-overs cricket," said Bailey of the 50-over team. "There is an enormous amount of skill and experience in the group which you need in a World Cup."

The World Cup squad will be slimmed down to 15 in early September.

Australia T20 squad:

Mitchell Marsh (capt), Sean Abbott, Jason Behrendorff, Tim David, Nathan Ellis, Aaron Hardie, Travis Head, Josh Inglis, Spencer Johnson, Glenn Maxwell, Matt Short, Steve Smith, Marcus Stoinis, Adam Zampa

Australia ODI squad:

Pat Cummins (capt), Sean Abbott, Ashton Agar, Alex Carey, Nathan Ellis, Cameron Green, Aaron Hardie, Josh Hazlewood, Travis Head, Josh Inglis, Mitchell Marsh, Glenn Maxwell, Tanveer Sangha, Steve Smith, Mitchell Starc, Marcus Stoinis, David Warner, Adam Zampa