American Chris Horner pulled away from team mate and compatriot Levi Leipheimer with about four kilometres remaining to win the fourth stage of the Tour of California on Wednesday and grab the overall lead.
Horner, who placed fourth in the event last year, completed the hilly 131.6 kilometre (81.8 mile) road race from Livermore to San Jose in three hours 27 minutes 51 seconds.
Twice Tour de France runner-up Andy Schleck of Luxembourg finished the stage in second with Australian Rory Sutherland close behind in third, despite being credited with the same time.
"I wanted to break the race apart," said the 39-year-old Horner, who placed 10th overall as the top American finisher in the 2010 Tour de France.
"Levi (Leipheimer) is the three-time champion and I was riding in support of him. I think we will still try to protect him. He's a big favourite in the time trial."
Leipheimer won the Tour of California for three consecutive years, beginning in 2007, largely because of his dominating time trial wins. After a one-year absence from the event, the 24 km Solvang time trial returns as stage six.
Horner, who began the fourth stage in 21st position, took over the race lead by 75 seconds over Leipheimer, who finished the day in fourth place.
Tom Danielson, also of the United States, was third overall, trailing by one minute 22 seconds.
Horner and Leipheimer, who ride for RadioShack, the American team partially owned by retired seven-time Tour de France titlist Lance Armstrong, began the final six-kilometre climb to the finish together.
But Horner powered away from his team mate after about two kilometres, quickly built his lead and was never challenged in the race's first ever mountaintop finish.
Schleck, who has finished second to Alberto Contador in the last two editions of the Tour de France, did not expect to be competing for a mountaintop stage win.
"All mountain stages are difficult, but this one was difficult because there was no place to recover," he said. "But I surprised myself. I didn't expect to be up there."
The Tour of California continues on Thursday with the 217.5 km road race from Seaside to Paso Robles, the longest stage of the event.