Kewell is unlikely to be fit in time for Australia's friendly against Holland on June 4th and is likely to miss the Socceroos' game with Liechtenstein three days later as well.
Kewell could go to the World Cup but find himself restricted to cameo appearances if he doesn't shake off this injury.
"I didn't play Harry in the second [qualifier] game from the start against Uruguay because he was in the same physical condition coming back from an injury. So it might be possible that he can be part of the game, but not from the start onwards," said Australia coach Guus Hiddink.
"But we'll see, it is a little bit early to judge now. Maybe we make a decision just after the Holland game."