(CNN) -- Ghana captain Stephen Appiah says the west African side will be ready for "war" when they face Australia at the World Cup in Rustenburg on Saturday.
Germany's shock defeat by Serbia on Friday means that another win for the Black Stars in group D would put them firmly on course for a place in the last 16, following their 1-0 win over Serbia in their opening match.
Australia were beaten 4-0 by Germany in their first game but Appiah and teammate John Mensah said they would not be taking the Socceroos lightly.
"Every country has their own style of play and the Australians are physically and mentally strong," Appiah told CNN. "It's going to be a war, it's not going to be a football game. It's going to be really tough, but we're ready -- it's no problem."
Defender Mensah said Australia were a better team than their heavy defeat by Germany suggested.
"Just because they lost to Germany, that doesn't mean they're not good," Mensah told CNN. "We don't underrate this Australian team. We will have to fight hard to get the three points."
Appiah said Ghana had benefited from the support of the South African fans and said there was "unity" between all the African sides at the first World Cup to be held on the continent.
"We are all excited to be in Africa to participate in this World Cup and we all hope to support African teams who are still playing," said Mensah.
Ghana are without their best player and regular captain Michael Essien but Appiah said the Chelsea star was in touch with the squad every day. And he said the team could still do well, citing Ghana's run -- without Essien -- to the final of the Africa Cup of Nations in Angola.
"He is one of our key players.... But it doesn't mean that if one guy is not there the team is finished," Appiah said.
Appiah admitted that the official Jabulani tournament ball was proving difficult to get used to but he said it would be good for players, with goalkeepers being caught out by its unpredictable movement.
"This football is a little bit strange and it's difficult when you get a long pass ... it's kind of swerving, so you don't know where the ball is going," he said. "A lot of goalkeepers are complaining about this ball."
Despite beating Serbia, Appiah said the Ghanaians would not be getting carried away.
"Let's enjoy this moment and we will see what happens in the future," he said. "We proved to the world that we know how to play football."