Australia has claimed a comfortable victory over Sri Lanka at the Cricket World Cup, winning by 87 runs at The Oval.

Aaron Finch's magnificent 153 and a quick-fire 73 from Steve Smith helped guide Australia to a mountainous total of 7-334, although some disciplined death bowling from Sri Lanka deprived the Aussies of total that had threatened to exceed 350.

Not achieving that goal could prove problematic against the leading contenders at this World Cup, but Sri Lanka was unable to capitalise on any possible sign of weakness, despite a rapid start to its chase.

Sri Lanka exploded out of the blocks as Kusal Perera and Dimuth Karunaratne each made 50 inside 14 overs.

However, wickets at vital times throughout the innings stymied the Sri Lankan chase to hand the Australians a fourth victory from five games at this World Cup.

Sri Lanka meanwhile suffered its second defeat after two consecutive washouts to severely dent its chances of progressing to the semi-finals.

Australia goes top of the World Cup table with the win, however the likes of India and England have played fewer games.

Kusal Perera made a rapid 52 before being bowled by Mitchell Starc. ( AP: Kirsty Wigglesworth )

Finch masterclass sets tough total

Australia started its innings brightly, with skipper Finch and David Warner laying the foundations for a massive total with an 80-run partnership at the top of the innings.

Despite the overcast conditions, none of the Sri Lankan bowlers could extract much movement in the air, and Finch in particular capitalised down the ground.

Finch's 50 came off just 53 balls by virtue of a suite of exquisite straight and cover drives that flew to the boundary off the bowling of Nuwan Pradeep and Lasith Malinga.

Lasith Malinga did not trouble Finch, claiming just one wicket in the innings. ( AP: Kirsty Wigglseworth )

The Australian captain said he would have likely chosen to bat first as well, but it appeared the decision being taken out of his hands was the best outcome after he lost the toss once again this tournament.

Off-spinner Dhananjaya de Silva proved an unlikely strike bowler in the middle overs, claiming the wicket of Warner for a relatively sedate 26 off 48 balls in just his second over.

Warner missed a straight one attempting a cut shot far too close to his body, only to see the ball fly unimpeded into the top of his middle stump.

Khawaja, whose status at number three has so often been victim of circumstance during this World Cup, was then unable to capitalise when called upon first drop, making just 10 runs off 20 balls before skying a slog sweep to Isuru Udana in the deep.

Having scored just 40 runs between the 11th and 20th overs, Australia needed to regain the impetus, and former skipper Steve Smith was the man to provide the spark.

The partnership between the pair reached 150 off just 111 balls, their idiosyncratic styles making for compelling viewing as the balls flew over the ropes and into the crowd.

Finch's century came off 97 balls, reaching the milestone with a huge drive for six runs, his 150 with a similarly expansive shot for four.

Steve Smith looked so comfortable he could bat with his eyes closed. ( AP: Kirsty Wigglesworth )

Smith made his half-century a short time later, reaching his landmark off just 46 balls as Australia accelerated towards an imposing total.

Finch departed after equalling his highest ODI score of 153 after miscuing a drive to cover to Karunaratne.

That happened in the 43rd over with Australia ideally placed on 273, only to stutter and stumble towards the end of the innings.

Smith departed for a well-paced 73 next over, victim to a magnificent slower-ball yorker from one of the world's greatest exponents of the art of death bowling, Lasith Malinga.

Maxwell plundered 22 runs off the 45th over, but it was just a brief riposte from the Sri Lankan comeback.

Either side of two more spartan Malinga overs, Shaun Marsh fell after holing out for 3.

Next up, Carey was run out by Udana, who slid, turned and threw down the stumps in one motion.

Udana repeated the trick two balls later to dismiss Pat Cummins for a first-ball duck.

The final total of 335 was more than enough, but against sides with stronger batting line-ups Australia looked like it could be made to pay for its costly hesitation at the death.

Sri Lanka make rapid start before falling away

Sri Lanka captain Dimuth Karunaratne attempted the anchor the innings, but his dismissal sparked a collapse. ( AP: Kirsty Wigglesworth )

Early in the Sri Lankan innings, it appeared as though the Australians would be in trouble.

Perera in particular looked in brilliant touch, belting the Australian attack to all corners as he raced to a 33-ball 50.

However, his 36-ball onslaught came to an abrupt end when he played all around a straight Mitchell Starc delivery that took the top of his middle stump, ending a 115-run partnership with his captain Karunaratne.

That wicket put the brakes on Sri Lanka's chase, with the run rate slowing to a crawl as Glenn Maxwell exerted some control with his off breaks.

Thirimanne never really got going, falling to a Jason Behrendorff delivery that he feathered through to Alex Carey behind the stumps for 16.

The Sri Lankan innings was hanging by a thread, with Karunaratne labouring towards his century as the dot balls stacked up.

Pat Cummins secured a vital wicket in the Sri Lankan innings. ( AP: Kirsty Wigglesworth )

With pressure mounting, and already on his highest ODI score, Karunaratne blew his chance at a century, cutting straight to Maxwell at point to fall just three runs shy.

The Sri Lankan innings fell apart quickly after the loss of their captain, with Angelo Matthews (9), Milinda Siriwardana (3) and Thisara Perera (7) falling within the space of nine balls thanks to Cummins and Starc.

When Kusal Mendis nicked off to Carey for 30 off the bowling of Starc the next over to put the quick on a hat-trick, the game was truly up.

Isuru Udana was caught by a rapidly backpedalling Finch in the deep for 8, with Malinga following shortly after for 1 both off the bowling of Richardson.

De Silva provided some brief resistance at the end with some wild swings that fell agonisingly short of the fielders, however Pradeep was unable to provide the same level of resistance, edging behind off Cummins for a seven-ball duck.

See how all the action unfolded in our live blog.