Australia captain Aaron Finch led by example, hitting a masterful century to put the World Cup holders in control of Saturday's match against Sri Lanka at the Oval.
Finch reached his ton in 97 balls with eight fours and four sixes, bringing up his hundred with a maximum off Milinda Siriwardana.It was his 14th one-day international century and the second of his World Cup career.
With Finch in peak form, Australia moved onto 190 for two after 34 overs as they chased a big score to put Sri Lanka under pressure.
Australia are searching for their fourth win in five matches after beating Afghanistan, the West Indies and Pakistan, with their lone defeat coming against India.
Together with opening partner David Warner, Finch carved up the rusty Sri Lanka attack after being put in to bat under cloudy skies in south London.
Three sloppy pieces of Sri Lanka fielding in the space of eight balls led to six extra runs for Australia.
Finch and Warner were already well on top without Sri Lanka's mistakes and they reached their 50 partnership in 57 balls.It was their fourth opening stand of at least 50 in the tournament and their 19th in all ODIs.
Finch survived an lbw replay review when he was on 35 as he progressed serenely towards his century.
Warner was the first Australian to perish when he was bowled by spinner Dhananjaya de Silva for 26.
De Silva struck again when Usman Khawaja (10) played a loose shot straight down the throat of Isuru Udana at deep square leg to leave Australia 100-2.
That brought Steve Smith to the crease and triggered the now-standard smattering of boos from the non-Australians in the crowd in reference to his role in the ball-tampering scandal in South Africa last year.
But Smith has been in fine form since returning from his ball-tampering ban and his presence freed Finch to go for broke.
Finch stepped on the gas to take 20 runs, including two sixes, off De Silva's eighth over.
Sri Lanka's previous two matches against Pakistan and Bangladesh had been abandoned due to rain, meaning they were back in action for the first time in 11 days.
That frustrating down-time allowed grievances to fester and team manager Ashantha de Mel took a swipe at World Cup organisers for allegedly giving preferential treatment to other countries.
De Mel blasted the quality of pitches, practice facilities, transport and accommodation at the World Cup, prompting a stern defence from the International Cricket Council.
Crushed by New Zealand in their opening game, Sri Lanka had bounced back to beat minnows Afghanistan in another rain-affected clash.