Haussler was involved in a breakaway and went on to win

Haussler powered ahead of Swiss rider Martin Elmiger and Spaniard David Latasa to cross the line in three hours 20.26 minutes on Friday.

Tour leader Roberto Heras finished in the main peloton 15 minutes later to maintain his overall lead.

The Spanish rider is chasing an unprecedented fourth straight title.

Stage 18 results:
1. Heinrich Haussler (Germany / Gerolsteiner) 3:20:26"
2. Martin Elmiger (Switzerland / Phonak) same time
3. David Latasa (Spain / Comunidad Valenciana) same time
4. Juan Fuentes (Spain / Lampre - Caffita) +10"
5. Constantino Zaballa (Spain / Saunier Duval) +30"
6. Pablo Lastras (Spain / Illes Balears) +43"
7. Jose Miguel Elias (Spain / Relax) +45"
8. Linus Gerdemann (Germany / Team CSC) +50"
9. Roberto Laiseka (Spain / Euskaltel) +54"
10. Fabio Baldato (Italy / Fassa Bortolo) +2:16"

Overall standings:
1. Roberto Heras (Spain / Liberty Seguros, 78 hours, 6 minutes, 39 seconds.
2. Denis Menchov, (Russia / Rabobank) + 4:30
3. Carlos Sastre (Spain / CSC) + 4:50
4. Francisco Mancebo (Spain / Illes Balears) + 5:48
5. Carlos Garcia Quesada (Spain / Comunidad Valenciana) + 6:22
6. Oscar Sevilla (Spain / T-Mobile) + 11:13
7. Ruben Plaza (Spain / Comunidad Valenciana) + 11:36
8. Juan Miguel Mercado (Spain / Quick Step) + 15:28
9. Tom Danielson (United States / Discovery Channel) + 15:50
10. Mauricio Ardila (Colombia / Davitamon Lotto) + 15:53