Reigning MotoGP World Champion Jorge Lorenzo has admitted he is going to have a hard time at this weekend's Phillip Island round as he says series leader Casey Stoner is invincible at his home circuit.

Lorenzo has a 40-point gap to make up in the final three races if he is to retain his crown at an Australian circuit that he favours but may have to settle for a podium behind the seemingly-uncatchable Stoner.

“I am now heading to Australia after a few days of training in Indonesia. I’m looking forward to riding at the Phillip Island circuit, one of my favourite and probably the most beautiful track we race on," said Lorenzo.

"After the race in Japan, where we had a positive result, we are really determined to be on the podium again. We know it's not going to be easy because Casey is usually invincible on his home track, but I will try my best and won’t give up.”