Latest results

The Liberty Seguros ace took the 217km leg from Cuenca to Valdelinares in five hours, 27 minutes and 20 seconds.

Russian Denis Menchov was second and Spain's David Blanco third - but USA's Floyd Landis abandoned the race.

Heras, Tour winner in 2000, 2003 and 2004, now leads the overall standings by six seconds from Menchov.

Heras shook off Menchov with just under two kilometres to go to the summit finish.

But the Category One climb proved too much for Landis.

The Phonak rider had been a pre-race favourite but after Wednesday's stage he ranked a disappointing 92nd in the overall standings, nine minutes 33 seconds behind the then leader Bradley McGee of Australia.

Stage six results:

1. Roberto Heras (Spain / Liberty Seguros) 5:27:20"
2. Denis Menchov (Russia / Rabobank) +13"
3. David Blanco (Spain / Comunidad Valenciana) +28"
4. Carlos Quesada (Spain / Comunidad Valenciana) +42"
5. Juan Miguel Mercado (Spain / Quick-Step) +49"
6. Francisco Mancebo (Spain / Illes Balears) same time
7. Carlos Sastre (Spain / Team CSC) same time
8. Jakob Piil (Denmark / Team CSC) +52"
9. Marcos Serrano (Spain / Liberty Seguros) +1:15"
10. Michele Scarponi (Italy / Liberty Seguros) same time
11. Joaquin Rodriguez (Spain / Saunier Duval) +1:22"
12. Manuel Beltran (Spain / Discovery Channel) same time
13. Gilberto Simoni (Italy / Lampre - Caffita) +1:40"

Overall classification:

1. Roberto Heras (Spain / Liberty Seguros) 23:42:13"
2. Denis Menchov (Russia / Rabobank) +6"
3. Carlos Sastre (Spain / Team CSC) +1:01"
4. Joaquin Rodriguez (Spain / Saunier Duval) +1:03"
5. David Blanco (Spain / Comunidad Valenciana) +1:05"
6. Francisco Mancebo (Spain / Illes Balears) +1:20"
7. Carlos Quesada (Spain / Comunidad Valenciana) +1:33"
8. Juan Miguel Mercado (Spain / Quick-Step) same time
9. Unai Yus (Spain / Bouygues Telecom) same time
10. Michele Scarponi (Italy / Liberty Seguros) +1:52"