ASPEN, United States (AFP) - US ski star Lindsey Vonn crashed out in the first run of the giant slalom on Friday at her home nation Alpine Ski World Cup event.

Four-time World Cup champion Vonn, 31, was running seventh when she faltered, the third of 18 skiers who failed to finish the opening run.

"My left ski came off," Vonn said.

"To be honest I am a bit perplexed. It wasn't even bumpy. It never happened to me in a race before. To happen in Aspen is really disppointing."

That sends Vonn forward to next week's speed events in Canada, a course where Vonn has dominated in past seasons.

"Next week, it's Lake Louise," she said. "I am going to move from today and focus on that."

Vonn said she felt good and confident even though much of her focus has been on the speed events in pre-season work.

"It is just super annoying," Vonn said. "Before that I felt very good. I haven't trained a lot of GS over the last weeks as I missed Chile and focused on speeds.

"I was a bit nervous. GS is not my strongest event. I am not as confident as I should be maybe. It took me a couple of gates to come into it. Once I hit the flat, I got in a good rhythm. I started to attack."