Australia have set up a winner-takes-all Rugby Championship showdown with New Zealand after thrashing Argentina 34-9 in Mendoza.

The Wallabies moved to the top of the competition ladder, ahead of the All Blacks on points differential with both teams unbeaten in the opening two rounds.

The title will be decided at Sydney's ANZ Stadium on August 8, with the home side looking for their first trophy since 2011.

Skipper Stephen Moore said his team watched the All Blacks fight back to overcome South Africa before their own game and knew it would be massive challenge.

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"They were fantastic and they showed why they're the best team in the world at the moment so it's a huge challenge for us," Moore said.

"There's plenty to work on so that game's going to be a big test for us."

Despite the impressive final scoreline, the Wallabies only led 8-6 at halftime.

A 60th-minute try scored by reserve lock Dean Mumm, who shrugged off three defenders to touch down, proved decisive.

Kurtley Beale also came off the bench to light up the attack, with the Wallabies snatching the vital bonus point after Tevita Kuridrani and Adam Ashley-Cooper crossed in the dying minutes.

Winger Joe Tomane opened their account in the first half after some handy lead-up work by Israel Folau.

Looking to avenge last year's four-point loss to the Pumas at the same venue, the Australians started brightly enough.

But they lost inside centre Matt Toomua after eight minutes when he took a head knock tackling his opposite Juan Pablo Socino and was unable to return.

Wallabies coach Michael Cheika made the unusual decision to replace him with Quade Cooper rather than Beale, who played there all Super Rugby season.

Cooper never really settled and then found himself yellow-carded for a late and high shot on Pumas five-eighth Nicolas Sanchez.

Cheika admitted the performance wasn't pretty but was happy his team were able to grind out the solid win.

"We just stuck at it," he said.

"I didn't expect that margin and I don't think it was reflection of the game.

"We weren't perfect by any means but we kept doing what we were doing and kept playing consistently over the match and pushing Argentina into making mistakes."

Like in Brisbane when they edged South Africa, there were some things to like, particularly the impact of flanker David Pocock in his first start since 2012.

"I thought he was excellent," Cheika said.

"He took a few opportunities on the ball and made a few runs so he's improved his ball carry this year immensely."

Australia's scrum was put under heavy pressure by the Pumas, particularly in the first half with James Slipper and Greg Holmes packing down.

The team also gave away too many silly penalties including having two reversed.

But Moore said he thought the Wallabies forwards delivered a better showing than against the Springboks.

"It was a good contest," he said.

"Our lineout was pretty solid and we got some pay with our maul at the back end of the game, which was pleasing and the guys who came on did a great job for us."