Roberto Heras moved closer to a record fourth Tour of Spain title when he seized the overall lead with victory on the sixth stage, the mountains proving too much for Australian Bradley McGee.

The Spanish Liberty Seguros rider shook off the entire field on the day's final nine kilometre climb to secure his ninth career stage win in the Tour of Spain.

Russian Denis Menchov was the last rider to buckle under the strain of Heras's acceleration, finishing 13 seconds behind on the 217km run from Cuenca.

Spaniard David Blanco was third, 28 seconds back.

Heras now leads Menchov in the overall standings by six seconds with Spaniard Carlos Sastre third overall, one minute further adrift.

McGee had led for the past four days but was more than 11 minutes down on Thursday's stage, finishing 87th.

He dropped to 60th overall, 10:45 behind Heras.

"I never expected to move into first place so soon," the 31-year-old Spaniard said. "But there was barely a metre of flat today, and it was over 200 kilometres long, so a lot of riders were exhausted even before the final climb."

Heras thanked his Liberty Seguros team mates for keeping such a high pace on the last climb, meaning the leading group was down to eight with four kilometres to go.

"Then a kilometre later, when I attacked, I just had to finish off their hard work," Heras said.

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