A key goal of new Twenty20 captain Mitchell Marsh is to keep Australia "nice and relaxed" as they strive for an unprecedented triple crown of titles across the game's three formats at the World Cup.

The laid-back allrounder headlines an experienced and settled 15-man squad for the June tournament, looking to make amends for their failure to reach the knockout rounds on home soil at the last event in 2022.

Marsh's formal appointment as skipper this month to replace the retired Aaron Finch caps a transformation from one of Australia's most pilloried players to one of its most respected.

Long earmarked for greatness, he made his international debut at 19 in 2011 and was appointed Test vice-captain after the infamous ball-tampering scandal in 2018.

But Marsh was then dropped from all formats of the game and lost his national contract due to a string of failures.

Now very much back in favour, chief selector George Bailey is confident he can inspire Australia to match their exploits as the current one-day and Test world champions.

Those achievements came under Pat Cummins, who is in the squad but opted out of the captaincy.

"I think he's just got the natural characteristics of someone who is very genuine (and shows) good care around others," Bailey said of Marsh, whose father Geoff and brother Shaun both played for Australia.

"Performance is obviously a really important one too from your captain, from your leader. You want them to lead from the front. I think Mitch has done that particularly well in T20 cricket over a period of time."

Marsh has no plans to rock the boat in the West Indies and United States, instead making it his mission to keep the team relaxed off the field and fired up on it.

"One of the biggest things I've learned is to not change too much," he said.

"A lot of preparation and planning goes into a World Cup, but once we're there it's about keeping everything nice and relaxed, keeping the environment good and making sure we give it our all."

"I think we've got a really great squad, a lot of versatility, a lot of experience and that brings a lot of excitement," he added.

Marsh, 32, has no shortage of experienced heads to ask for advice, should be need it.

His "great mate" Cummins and wicketkeeper Matthew Wade both have captaincy experience, while veteran opener David Warner -- in his international swansong -- is never afraid to offer an opinion.

Big moments 

But former skipper Steve Smith failed to make the squad.

In his absence, Warner and Travis Head are set to open with Marsh at first drop, with Tim David and Glenn Maxwell the big-hitting finishers, barring injuries.

Cummins, Mitchell Starc and Josh Hazlewood again lead the attack alongside wrist spinner Adam Zampa, although the medium pace of Nathan Ellis is an option should the selectors need an alternative.

While England won the last World Cup and Australia were champions in 2021, Marsh insists there are no favourites.

"If you look at this tournament now and the teams around the world, I don't think there can be a favourite," he said.

"There's five, six or seven teams that can win it and we know that in tournament play it's all about getting things right at the right time and winning in big moments, and that will be a key focus for us.

"The game's moving forward, it's evolving, teams have been going harder in the power play, that's been a real trend. But it's about getting on the ground and assessing conditions and we'll play as we see it."

No team has been T20, ODI and Test world champions at the same time, but Marsh is adamant it is too early to think about such a lofty achievement.

"There's so many things you have to get through at a World Cup before you even get a crack at that, so that's probably for the external noise outside of what we are trying to do as a group," he said.

"But the carrot is there."

Australia are in Group B alongside England and open their campaign against Oman in Barbados on June 6.