Klemmer came off the bench in the Kangaroos’ 14-8 victory over New Zealand at the Ricoh Arena.
The 22-year old, who made his Test debut two years ago, has been impressed as a substitute against Scotland and the Kiwis.
Asked if he now belonged at Test level, Klemmer admitted he can’t afford to be complacent in this Australian side.
“I don’t think you can be comfortable in playing in teams, you’ve always got to strive for better and you’ve just got to keep doing your job,” the prop said.
“You just can’t relax because there’s always someone there to take your spot so you’ve just got to keep playing good footy and never try and relax because it could be your last game.”
Klemmer impressed as an interchange forward against the Kiwis.
The 198cm and 120kg Bulldogs front-rower is bracing for another tough battle against England in London.
“They’re a world-class forward pack and hopefully we get the nod and the opportunity to play next week,” he said.
“As a forward pack we try and do our best every week and that’s all we can do.”
“We gave the Kiwis side a lot of ball [in Coventry] and that’s what got them back in the game so we’ll move on to England and hopefully the final.
“Play a bit better and control the footy a bit more.”