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The star batsman said the problem could recur at any time.
"I'm taking the best medical advice and I'm doing everything I can to face Australia but, occasionally, achilles injuries do flare up," Pietersen was quoted as saying in the Guardian.
"If that happens on the morning of a Test then I wouldn't be able to take part."
Pietersen was ruled out of England's World Twenty20 defeat by Holland but has played in England's subsequent matches in the tournament. The injury is related to a nerve problem in his back.
"I can promise you I am doing everything in my power to make sure I am ok," he said.
"I've got one more injection I can have before I'm not allowed any more. That would be a cortisone epidural into the spinal cord.
"There is still pain in the heel but I'm doing the right thing to try to eliminate as much pain as I can.
"In order to fix an achilles injury like this properly, I probably do need two or three months out of the game. Unfortunately, that's not going to happen. I'm a man who wants to play every game for England and as much as I can. As long as I can walk I will play."