Reigning Olympic downhill champion Lindsey Vonn has admitted defeat in her battle to recover from injury and defend her title in Sochi next month.
Vonn has been struggling to recover from a serious right knee injury she sustained in the first race of the 2013 World Championships in Schladming last February.
The American returned to snow in August but suffered a setback during training in November and has now acknowledged the Games will come too soon.
In a statement posted on her official website, Vonn said: "I am devastated to announce that I will not be able to compete in Sochi.
"I did everything I possibly could to somehow get strong enough to overcome having no ACL but the reality has sunk in that my knee is just too unstable to compete at this level.
"I'm having surgery soon so that I can be ready for the World Championships at home in Vail next February.
"On a positive note, this means there will be an additional spot so that one of my team-mates can go for gold. Thank you all so much for all of the love and support. I will be cheering for all of the Olympians and especially team USA!"
Vonn has won four overall World Cup titles and six consecutive downhill season titles, including in her injury-abridged 2013 season.
She tore her anterior cruciate ligament in her crash at Schladming, and re-tore the ligament during training in November.
Despite her setbacks Vonn consistently maintained her belief that she would recover in time to defend her title, but had struggled since returning to competition last month.