Paula Radcliffe was on the way to her French training base today to begin her bid to defy medical opinion and win Olympic gold. Radcliffe, who was thought to be suffering from a hip injury, has been told that her problem is a low-grade stress fracture to her femur and that it will be "impossible" for her to run in Beijing. But the British world record holder is determined to make the starting line for the Olympic marathon on 17 August.

"I'm giving it an extra week on crutches. I will be in the pool at the weekend and, hopefully, I'll be running again in less than a fortnight," she said. "If there was a fracture it has already healed but we need to wait for the bone to harden up.

"I'm doing everything I can to accelerate the healing and that is generally a two-week period."

Radcliffe's last competitive outing was in November and, after missing April's London Marathon with a toe injury linked to her current problem, she will arrive in Beijing on the back of nine months without a race.

But the 34-year-old added: "I've never had a problem coming out after a lay-off and I'm going to be extremely hungry.

"Things have been very frustrating. No one really seems to be able to explain how it happened.

"There's a huge amount of frustration. I could have been on crutches earlier rather than walking around on it.

"Maybe I should have stamped my foot a bit harder for a bone scan to rule it out earlier."

Radcliffe is desperate to make up for the disappointment of not finishing the marathon in Athens four years ago.

"I know it's not going to be easy, I know I need to take certain risks and a bit of luck. But I think it's possible."

Meanwhile, American 100metres world champion Tyson Gay is to race against Jamaica's world record holder Asafa Powell for a £25,000 prize at the Aviva London Grand Prix at Crystal Palace on 25 July. But they may also have to take on Usain Bolt, the Jamaican who earlier this month ran the second-fastest 100m of all time.