Radcliffe missed the London Marathon with a toe injury
Marathon world record holder Paula Radcliffe is refusing to rule out running at the 2008 Olympics despite suffering a stress fracture to her leg.
The Briton, 34, was diagnosed with a low-grade injury to her left femur following an MRI scan on Wednesday.
Despite describing the news as a "bombshell", she insisted she is "90-100% likely" to run in Beijing.
"It's going to go down to the wire and I will need a bit of luck, but I'm not giving up," Radcliffe said.
"I won't run through pain and I won't go if I can't be competitive. It's not ideal but I'm trying to stay positive."
Radcliffe revealed she had been told by specialists it would now be "impossible" for her to complete enough training to be fully fit for Beijing.
She said: "Everything has been with Beijing in mind, it's been a huge focal point and it's hugely important to me."
Radcliffe admitted she was "angry" the problem had not been correctly diagnosed earlier despite two MRI scans, one in Germany and one in England.
"There's a huge amount of frustration," she said. "I could have been on crutches earlier rather than walking around on it."
Radcliffe hopes to start running again in a fortnight and will be swimming and cross-training at her base in France in the meantime.
"I'm doing everything I can to accelerate the bone healing and that is generally a two-week period," she added.
Radcliffe will be working with a team of medics and physiotherapists to ensure she gives herself the best possible chance of competing in Beijing.
However, BBC Radio 5 Live athletics commentator Mike Costello said Radcliffe's chances of being competitive in Beijing were "slim".
"If this was the World Championships or any other event apart from the Olympics, she wouldn't be going for it, in all likelihood," he said.
"But it is the Olympics. She has been three times in the past and never won a medal.
"It may well be she is the only person who believes she can make it to Beijing, but it's that attitude that has made her what she is and who she is."
Sports physician Dr Kalpesh Parmar told BBC Sport that a stress fracture was a "disaster"' for Radcliffe.
"It's difficult to know without seeing the scans or the patient, but if it's a stress fracture to the femur it's a minimum of six weeks for the leg to heal," he said.
"She will also be deconditioned, so will need a similar length of time even after the injury has healed. A fracture could keep her out for a long time.
"If it's bone stress as opposed to a fracture, then it won't necessarily be as long, but if she has been running with pain it could be symptomatic."
Radcliffe believes the bone could heal in two weeks, but Dr Parmar, of Pure Sports Medicine, added: "It sounds like she's being very optimistic. There are procedures we can do for bone stress, but not for a fracture."
Radcliffe had turned her focus to Beijing after her dramatic failure at the 2004 Games in Athens.
One of the favourites going into the race, she withdrew at the 23-mile mark.
She attempted to win a medal in the 10,000m just a few days later but dropped out of the final with eight laps to go, later revealing she had been suffering from a quad injury and a stomach upset.
This season her training schedule has already been disrupted by a toe injury on her right foot which first came to light when she finished runner-up in last September's Great North Run.
She went on to win the New York Marathon for a second time in November 2007, despite the niggling injury.
It flared up again while Radcliffe was altitude training in the USA in February, and she was forced to miss the chance to earn a fourth Flora London Marathon title last month.
Earlier this week she was named in the Great Britain marathon team for Beijing along with Mara Yamauchi, Liz Yelling and Dan Robinson.