Washington - Lance Armstrong's bicycle was stolen just hours after he rode it in a California race, but the US cycling legend was confident of getting it back - there's only one like it in the world.

Armstrong is racing in the nine-day California Amgen Tour, which started Saturday. His bicycle was stolen, along with three others from the Astana team truck.

"Whoa!! They just came to my room and said our truck was broken into and someone stole my time trial bike! APB out to the twitterati," said Armstrong, as he announced the bike theft on his Twitter account on Sunday morning and even posted a photograph.

"There is only one like it in the world therefore hard to pawn it off. Reward being offered," he wrote.

The stolen bicycle is not the one Armstrong rides during the race, CNN reported Monday, but is used only for time trials - where he trains over a fixed distance through staggered intervals to try and get the best time.

Armstrong finished fifth in the stage, which was won by Spain's Francisco Mancebo.

"Holy hell. That was terrible. Maybe one of the toughest days I've had on a bike, purely based on the conditions. I'm still freezing," he wrote on Twitter after the race.

Armstrong is racing in California as he attempts a comeback after retiring in 2005. He also intends to ride in this summer's Tour de France.

The seven-time Tour de France winner raced last month in the Tour Down Under in Australia, finishing 29th. (dpa)