Veteran striker Tim Cahill insisted Wednesday Australia are not at the World Cup to make up the numbers as they try to clamber out of a group containing champions Spain, the Netherlands and Chile.

"It's a real time for us to be tested. Hopefully we can make an impact -- football is all about earning respect," said Australia's all-time top scorer, now plying his club trade with Major League Soccer side New York Bulls.

"Why can't this be the best World Cup I am going to play in?" asked the 34-year-old, who scored twice in the 2006 group win over Japan and again in the 2010 event against Serbia.

"Why can't we be the best Australia a team ever? Some of these kids are pretty special," said Cahill, urging the squad to "stand up and be counted" despite their status as rank outsiders.

"We don't want to make it easy for anyone. We want them to come off the park and say 'I don't want to play that Australian team again,'" said Cahill ahead of Friday's final test against Croatia in Salvador.

"The best thing I can see from this group of players is the determination. For me the most important thing is everyone is together -- it's a nice training atmosphere, the boys are bouncing off each other well on and off the park," Cahill told reporters.

"Its a great feeling - there's no fear among these boys," said the former Millwall and Everton man who has netted 32 goals for the Socceroos to date.

Insisting he would not be in Brazil if he thought the team were not up for the challenge, Cahill said that the "focus now is a good performance against Croatia -- that will be a good test" ahead of Chile in Cuiaba on June 13.

Earlier, Australia's most capped player Mark Schwarzer had said he was worried about how inexperienced Ange Postecoglou's squad is.

But Cahill insisted they would react strongly to losing the likes of injured playmaker Tom Rogic, left out of the final 23.

"You've got to adapt to these situations," Cahill observed.

On his own longevity, he added: "Everyone knows I moved to the MLS to New York Red Bulls to prolong my international career -- it was a massive gamble. I love playing for my country.

"It's a privilege to be where I'm sitting," said Cahill, saying he hoped to bring his experience to bear and "I really want to lead from the front."