Marcus Stoinis smashed an unbeaten 59 off 18 balls to power Australia to a seven-wicket win over Sri Lanka and reinvigorate their Twenty20 World Cup defence on Tuesday.

Chasing 158 for victory, the hosts depended on Stoinis's rapid-fire knock to achieve their target with 21 balls to spare in Perth and bounce back from their opening hammering to New Zealand.

Next up for the hosts are old rivals England on Friday.

The Australians looked in a spot of bother at 89-3 but Stoinis came out all guns blazing to smash four fours and six sixes.

Skipper Aaron Finch, who made a laboured 31, looked a mere bystander in the unbeaten 69-run stand with Stoinis, who made the match his own.

Charith Asalanka had made an unbeaten 38 to guide Asian champions Sri Lanka to 157-6, a total that looked competitive until Stoinis arrived on the scene.

Sri Lankan pace bowler Binura Fernando left the field in the first over of Australia's chase as the island nation feared for another addition to their already long injury list at this tournament.

But the fast bowlers kept the Australian openers in check and spinner Maheesh Theekshana got the big wicket of David Warner on his first ball after the left-hander gave away a catch to the fielder at cover.

Mitchell Marsh took stock and then attempted to break free with a four and six off Wanindu Hasaranga, but his extra aggression got him caught at long-off for 17.

Glenn Maxwell hit back with fours and sixes before he survived a nasty bouncer from Lahiru Kumara -- the ball caught his throat but after help from the physio the Australian got gingerly back on his feet.

Ashen Bandara dropped Finch on 23 but soon made up with a good catch at the boundary rope to help dismiss Maxwell, as bowler Chamika Karunaratne and Sri Lanka celebrated.

But the joy was shortlived as Stoinis took the game away from Sri Lanka with his bludgeoning knock.

Earlier, Australia elected to bowl first and replaced Covid-hit Adam Zampa with Ashton Agar in the team which lost their opener to New Zealand by a hefty 89 runs.

Sri Lanka looked in trouble at 120-6 in the 18th over but the left-handed Asalanka's 25-ball knock helped put up a fighting total.

Pathum Nissanka (40) and Dhananjaya de Silva, who made 26, put on 69 runs to lay the foundations for the total but Sri Lanka slipped midway by losing wickets.

Sri Lanka lost their sixth wicket in Hasaranga, but Asalanka stood firm and put on an unbeaten stand of 37 with Karunaratne, who made 14.

The pair smashed Pat Cummins for two fours and a six in a 20-run final over to finish with a flourish.

Cummins, Josh Hazlewood, Mitchell Starc, Agar and Maxwell took one wicket each.