By Neal Rogers

After four years of racing in February, the 2010 Amgen Tour of California will be held May 16-23, during the same time slot as the Giro d’Italia.

America’s biggest stage race will move from its winter dates into the spring, taking dates on the UCI calendar occupied this year by the Volta Ciclista a Catalunya ProTour event.

The race’s organizers discussed potential dates in April, May and June with the UCI road commission before deciding on the late-May time slot, a source close to the matter told VeloNews, adding that the Amgen Tour of California will not be a ProTour event in 2010, but will be starting in 2011.

Asked for comment Wednesday, Andrew Messick, president of race owner AEG Sports, said only, “it’s premature to make that announcement.”

Levi Leipheimer, the race’s three-time winner, said he was excited about the change.

“I think we can expect some big mountain climbs now that the ToC is in May,” Leipheimer said in an email to VeloNews. “I wouldn’t be surprised to see even bigger crowds as well, due to the better weather and classic mountain stages we normally see in a Grand Tour. I’m excited about this change, I know Santa Rosa is gearing up for another year.”

Leipheimer, who is currently in Italy for the Giro d’Italia, has won the race three years consecutively after American Floyd Landis won the inaugural event in 2006.

After the race’s first two years were held in sunny, warm weather, the last two editions have been marked by harsh winter weather, precipitating the calendar move.

With the date change, the race will have the option to travel into California’s mountains, including the Lake Tahoe area and the High Sierras.

Although the California race will conflict with the world’s second-biggest race, the date change will allow riders preparing for the Tour de France to recover from the spring classics season, race in California, and return to Europe to prepare for June’s Tour de France warm-ups, the Critérium du Dauphiné Libéré and the Tour de Suisse.

The 2009 edition of the Tour of California was the race’s longest, with a prologue and eight stages, and reached its highest elevation in four years when the race crossed over the 5000-foot summit of Palomar Mountain, near San Diego, on the final stage.