Harry Kewell believes Australia will benefit from a strong start when they tackle Germany in the World Cup opener on Sunday (Monday morning AEST).

The Galatasaray star says it is important for the Socceroos to really put the foot down early in the group stage otherwise it could end badly.

Kewell added that there is plenty optimism coming out of the Australian camp despite coming up against one of the tournament favourites.

"I think it's important to get off to a fly at the World Cup, to get three points, so I think let's face it we've probably hit the hardest team in the World Cup to come up against, especially first off the bat," Kewell said.

"Everyone's looking for these angles against the Germans they're a young team, they need to go forward but let's not forget when it comes to a big tournament they're always the favourite."