Landis broke his hip while training in 2002

The Phonak rider, second in the overall standings, needs surgery on his right hip after a crash in January 2003.

"I want to prove what I am capable of," said the 30-year-old. "Then it will be time for me to ride without pain."

Phonak team doctor Denise Demir said Landis refuses to take any pain medication, revealing: "He doesn't want it. He says it makes him tough."

Landis had pins inserted in his right hip and has since had two more surgical procedures - the last in 2004 - to try to restore blood to the bone.

But his right leg is now two centimetres shorter than his left leg as a result of the crash, when the ball at the top of the hip bone snapped off.

It's hard to quantify what pain is Floyd Landis

Demir added that when she first saw X-rays of his hip condition, she "couldn't believe that he could walk, let alone ride".

She also revealed that Landis cannot push the right pedal with the force that he can with the left.

Landis, a former team-mate of seven-time winner Lance Armstrong, said the pain is worse in time trials and climbing steep hills.

"It's hard to quantify what pain is," he said. "It's hard for anybody to understand what someone else is going through."

Landis is one minute behind race leader Serhiy Honchar. The Tour resumes on Tuesday with a flat stage from Bordeaux to Dax.