Australia coach Michael Cheika has named uncapped teenager Jordan Petaia and David Pocock in his World Cup squad, despite the forward's fitness concerns.

Pocock, 31, has not played for the Wallabies since November 2018 because of a calf injury but joins an experienced squad with back Adam Ashley-Cooper, who has 117 caps.

Fly-half Christian Lealiifano, who was diagnosed with leukaemia in August 2016, is also in the squad.

"I'm confident," Cheika said.

"We'll be a little bit unpredictable, that's been a little bit of our theme this year, if we don't know what we're doing no one will know what we're doing."

The two-time world champions will be captained by flanker Michael Hooper, 27, and take a squad with a total of 1,406 caps.

One of the most experienced players is versatile back Ashley-Cooper, 35, who is set to become only the second Australian to play at four World Cups after George Gregan.

Kurtley Beale, 30, is chosen at fullback in the absence of Israel Folau, who was sacked earlier this year, with Dane Haylett-Petty, 30, in as back-up.

Australia begin their World Cup campaign against Fiji on 21 September and go on to face Wales, Uruguay and Georgia in the pool stage.

The Wallabies reached the final of the 2015 tournament, but lost 34-17 to New Zealand.

Australia squad:

Forwards: Allan Alaalatoa, Rory Arnold, Adam Coleman, Jack Dempsey, Folau Fainga'a, Michael Hooper (captain), Sekope Kepu, Tolu Latu, Isi Naisarani, David Pocock, Izack Rodda, Rob Simmons, Lukhan Salakaia-Loto, Scott Sio, James Slipper, Taniela Tupou, Jordan Uelese.

Backs: Adam Ashley-Cooper, Kurtley Beale, Bernard Foley, Will Genia, Dane Haylett-Petty, Reece Hodge, Samu Kerevi, Marika Koroibete, Tevita Kuridrani, Christian Lealiifano, James O'Connor, Jordan Petaia, Matt Toomua, Nic White.