26/10/2015 10:34 AM AEDT | Updated 15/07/2016 12:50 PM AEST

Australia Must Be 'On Song' To Beat All Blacks, Mortlock says

SYDNEY-- Wallabies legend Stirling Mortlock has backed Australia to take out its third Rugby World Cup, but says the team will have to improve across the park to defeat reigning world champs New Zealand.

The Wallabies set up the mouth-watering RWC final with old-foe New Zealand after overcoming an enterprising Argentina 29-15 on Monday morning.

Adam Ashley-Cooper bagged three tries and was named man of the match in the win, which sent social media into overdrive including congratulatory tweets from Prime Minister Malcolm Turnbull and opposition leader Bill Shorten.

Mortlock, who played 76 tests for the Wallabies and captained the team 25 times, said Australia would need to take its game up a notch to beat the All Blacks, whom he said had been "fantastic" throughout the tournament.

"Both scrum and lineout need to be on song. Argentina were very good at unsettling both scrum and lineout" Mortlock told the Huffington Post Australia.

"We were fantastic at the breakdown and David Pocock was on fire and he combined very well with both (Scott) Fardy and (Michael) Hooper as well, we need to be on song there again."

He said the Wallabies' defence would also need to improve in the final.

"We had a lot of missed tackles and there was a stage when we lost our cohesion," Morlock said.

"Up against New Zealand they're number one in the world for a reason, they're world champions and they're in fantastic form, we need to be on song at our set piece, at the breakdown and we've got to be better at our defence.

Wallabies legend Stirling Mortlock believes Australia has what it takes to beat New Zealand in the RWC final

"If we have those areas firing then we're a good chance."

Australia's previous RWC titles came in 1991 and 1999, while New Zealand were 1987 and 2011 champions.

New Zealand, unbeaten in 12 consecutive RWC fixtures, will go into the final as favourites, while worries for Australia will be injury clouds over both Matt Giteau and Israel Folau.

Mortlock said Australia would likely have the mental edge going into next Sunday's match at Twickenham.

"The Wallabies will go into the game mentally in a pretty good state because this year in the Bledisloe Cup matches (they) played a really strong game in the Sydney one and thoroughly deserved the victory ," he said.

"Both New Zealand and Australia play each other so often, both teams have enough respect for each other that on a given day each team can rise to the occasion."

Mortlock joined fellow ex-Wallaby Michael Lynagh in tipping an Aussie victory.

"It'll be a massive game, I can't wait ... everything in me says Wallabies."