The result, and the resulting change in net run-rate, all but assures the victors of a semi-final berth.
Sri Lanka had started the match impressively, reducing Australia to 30 for four before a brutal knock of 85 not out from Cameron White lifted their total to 168 for five.
Australia ran rampant in the field, though, with Tillakaratne Dilshan‘s 20 the best of just three scores in double figures.
Dirk Nannes has proved one of the tournament’s standout performers with the ball and it was not long before he struck.
Mahela Jayawardene, himself on fine form in the competition, was the victim as his lofted pull found Steven Smith at fine leg.
That put Sri Lanka on 16 for one and only two more runs were added before Shaun Tait added the crucial wicket of captain Kumar Sangakkara, who went for two after gloving an attempted hook.
Sanath Jayasuriya had also struggled to get going and he had added just five in 14 deliveries when Nannes trapped him clean in front of the stumps.
Tillakaratne Dilshan eased a few nerves with a mighty six and two boundaries in a breezy 20 but he was next to go when White plucked a full-blooded cut out of the sky at backward point to give Mitchell Johnson a first success and leave the scoreboard reading 48 for four.
By now Australia were full of confidence and it was no surprise when Angelo Mathews departed for just eight, diverting Johnson to Mike Hussey in the covers.
Chamara Kapugedera pushed his way to 12 as Sri Lanka attempted simply to make a creditable total but he misread a flatter delivery from leg-spinner Smith and was bowled having nursed his side to 73.
Just 14 more runs were added for the next four wickets as the game was closed out in emphatic fashion.
First Nannes ran out Suraj Randiv with a direct hit from the deep, then Dinesh Chandimal fell for 19 as he came down the track to Smith and offered Brad Haddin a stumping chance.
Ajantha Mendis and Lasith Malinga managed just one run apiece before falling to Clarke and Johnson respectively to complete a miserable innings.
Australia’s innings was built around White’s monstrous 49-ball effort, which included six fours and as many sixes.
Mathews had earlier kicked things off by bowling Shane Watson via the inside edge in the first over of the day.
Fourteen runs came of the second but number three Brad Haddin did not last long.
He fell for a brisk 15 in Mathews’ next over, hoisting the all-rounder high in the air where Sanath Jayasuriya took a steepling catch.
Randiv turned the screw by removing David Warner (nine) and David Hussey (nought) in the same over to leave Australia 30 for four.
What followed was pivotal as White offered a half-chance off Randiv, only for the ball to narrowly evade the leaping Mendis.
Clarke did give the off-spinner a third success moments later as he lost his off bail but White, aided and abetted by the dependable Mike Hussey, took advantage of his life to set about some destructive hitting in the latter stages.
Australia: MJ Clarke (Captain), DJ Hussey, CL White, MEK Hussey, SPD Smith, MG Johnson, SW Tait, DP Nannes, S Watson, D Warner, B Haddin (WK).
Sri Lanka: TM Dilshan, DPMD Jayawardene, KC Sangakkara (Captain & WK), CK Kapugedera, AD Mathews, LD Chandimal, ST Jayasuriya, SL Malinga, BAW Mendis, S Randiv, UWMBCA Welegedara.