TWICKENHAM, London -- Australia will require "something special" to beat New Zealand in the Rugby World Cup final, Wallabies coach Michael Cheika says.

The Wallabies saw off Argentina 29-15 on Sunday with Adam Ashley-Cooper's hat-trick helping them book their place in the final. New Zealand's win over South Africa on Saturday means the trans-Tasman rivals will contest the Webb Ellis Cup for the first time.

Australia will monitor the fitness of Matt Giteau this week, who was forced off with a tight groin, and Israel Folau who was fatigued after fighting back from his ankle injury. And Chieka said post-match the Wallabies must improve if they were to prevail next weekend.

"New Zealand are the world's No.1 and they are there for a reason, I think we have only beaten them once in the last 10 games so they will be feeling pretty good that they have got our measure and we are going to have to do something special, something extra to just be competitive."

Stephen Moore said the Wallabies would have to play their "best game of the tournament next weekend" but Cheika, reflecting on their win over Argentina, was delighted by the team's support play as they put four tries on the Pumas.

"We have been guilty in the past of making breaks and not being there to finish so we have tried to work hard on that," said Cheika. "If we don't improve every week, we won't win.

"The one week we didn't really improve on our performance was the week before [the Scotland game] and so we have got to improve massively from what we did today to even be in the hunt next weekend.

"We are going to have to pick two or three things and try to make those things and support play is one of the things we have worked on hard."

"Every game at this level is so hard. They are very well drilled side, they have an excellent coach and are very organised so they know what they are doing all the time on the field from every situation. We have to be working hard all the time and believe in our own way of playing."