'This is the final'

Australia captain Michael Clarke will approach Friday's World Cup quarterfinal against Pakistan like a final, saying he expected a "tough challenge" from Misbahul Haq's men in the make-or-break game.

Pakistan have lost nine of their last 10 one-dayers to Australia on Australian grounds, including all of the last seven, but Clarke refused to take victory for granted.

"I think Pakistan have been under-rated for a long time especially in the shorter form of the game," Clarke told reporters at the Adelaide Oval on Thursday.

"They have got a lot of talent. Their attack is very good and they have got a good mix of youth and experience.

"It will be a tough challenge for us and I believe we have to be at our best to beat them. We'll treat this like a World Cup final.

"If you lose, you will be sitting and watching the rest of the tournament, so we are focused on just making sure we can have success in this game."

Four-time champions Australia beat England in their opening match, had a rained-out no-result against Bangladesh and then lost by one wicket to co-hosts New Zealand after being bowled out for 151.

They then won their three remaining matches to live up to their billing as one of the pre-tournament favourites.

However, Clarke said the results of the league matches were irrelevant and the momentum gained through the tournament will count for little if the team lost a knock-out game.

"When you walk out on the field tomorrow it's a new day. We all start on zero with the bat and zero with the ball as well," he said.

"What happened beforehand is irrelevant. It does not matter how well you have played earlier or what your plans are afterwards.

"It's about being 100 per cent focused and as well prepared as you can be; batting as well as you can, bowling as well as you can, and hopefully our fielding continues to be as good as it has been."