BRASSTOWN BALD — Kanstantin Sivtsov of Belarus, competing in the United States for the first time, pedaled to a surprising mountain stage win Saturday and became the fourth overall leader of the Tour de Georgia.

Sivtsov (High Road), 25, who began the day in eighth place six seconds behind Trent Lowe of Australia, suddenly advanced past the former race leader in the steep final half-mile to win the 88.4-mile Blairsville to Brasstown Bald Mountain sixth stage road race in 3 hours, 47 minutes, 16 seconds.

Lowe (Slipstream-Chipotle) was second, 10 seconds behind the stage winner.

Race favorite Levi Leipheimer (Astana) of Santa Rosa was third, 16 seconds behind Sivtsov With one stage of the 529-mile event remaining, Sivtsov holds a four-second lead over Lowe.

Leipheimer, who rode to a dominating win in the same mountain stage last year, is third overall, trailing Siutsou by 16 seconds.

"I waited and waited until the final half-mile; my teammates and team director told me it was the hardest part and just waited and waited," said Sivtsov, a former amateur world road titlist who lives near Bergamo, Italy.

Lowe, who assumed the race leader after the fifth stage, and Leipheimer, the reigning Tour of California champion who placed third in the 2007 Tour de France, were expected to vie for the stage that ended at 4,783 feet, the highest elevation in Georgia.

After finishing second in the stage, Lowe originally thought he had retained the overall race lead.

Nearly an hour later, race officials announced the results.

"He (Sivtsov) rode a strong race, but I was confident in my abilities and I rode at my limit," said Lowe, the former Australian national criterium titlist.

Lowe and Leipheimer exchanged aggressive riding tactics in the final two miles. But both riders underestimated Sivtsov, who finished 32nd overall in last year’s Tour de France.

"I think I made some mistakes, but it was a really tough call," said Leipheimer."

The severity of the sixth stage, the only mountain stage of the weeklong race, depleted the field. The bottom of the field finished 24 minutes behind the winner.

Despite his slim leading margin, it’s unlikely Sivtsov will lose his race lead in the final stage. The stage includes mid-stage and stage finish bonus seconds for top placings. But the time will likely be awarded to sprinters, not riders contending for the overall title.