Australia wing Adam Ashley-Cooper expects a stern test from Argentina in their Rugby World Cup semi-final, but admits he did not expect the Pumas to record such an emphatic victory over Ireland.

Daniel Hourcade's Argentina delivered an outstanding performance at the Millennium Stadium on Sunday to book their place in the last four, ultimately running out 43-20 winners against Ireland having led 17-0 inside 13 minutes.

Following Australia's dramatic 35-34 triumph over Scotland later in the day, courtesy of a controversial last-minute penalty from Bernard Foley, Ashley-Cooper reflected on the quarter-final ties and looked ahead to the Wallabies' next fixture.

Australia and Argentina will meet at Twickenham on Sunday, with the winner facing South Africa or New Zealand in the final.

"Obviously, New Zealand showed their class [when thrashing France 62-13]. South Africa were quite dominant [against Wales]," said Ashley-Cooper.

"I was surprised by the Argentina v Ireland result. For us it's just a matter of recovering now and addressing the areas we need to focus on.

"They have got a dominant forward pack and outstanding backs. We're going to have to look very closely at their game and formulate a strategy. I'm looking forward to getting excited for that semi-final."