Spain's Santiago Blanco won the 193.7km 18th stage of the Tour of Spain from Salamanca to the Covatilla ski station on Thursday.

Blanco launched an attack 43 kilometres from the finish and held on to win in a time of five hours, four minutes and 17 seconds.

Race leader Roberto Heras broke away from the main group with five kilometres to go but was unable to catch Blanco, finishing 40 seconds behind.

Heras' main rival for the gold jersey, his fellow Spaniard Aitor Gonzalez, could only finish eighth and now trails the US Postal rider by one minute and 12 seconds.

Blanco was born in nearby Puerto de Bejar and Heras in the village of Bejar, close to the foot of the Covatilla.

"If you don't attack you don't win. When I got to the Covatilla I was ready to die on the bicycle if need be, but I wasn't going to give up," said Blanco.

"Knowing the climbs well played out in my favour. I knew that the Covatilla got easier towards the top and that helped me keep going.

"This is a wonderful day for the people of this region, with me winning the stage and Roberto still wearing the gold leader's jersey."

Heras, who is assured of a hero's welcome when he starts Friday's 19th stage from his home village, is all but assured of overall victory.

But the final 41km time trial in Madrid on Sunday will give Gonzalez one last chance to challenge for the gold jersey.

"We won't know who the winner of this race will be until Sunday," said Heras.

"I've done well, but I can't help being impressed by Gonzalez's resilience."

Stage 18, Salamanca to Estacion de la Covatilla

1 S Blanco (Spa) iBanesto.com 5hrs 4mins 15secs
2 R Heras (Spa) US Postal Service at 40secs
3 J A Flecha (Spa) iBanesto.com at 0.47
4 J Beloki (Spa) ONCE-Eroski at 0.51
5 P Caucchioli (Ita) Alessio at 1.09
6 F Garcia Casas (Spa) Bigmat.Auber 93 at 1.10
7 O Sevilla (Spa) Kelme-Costa Blanca at 1.16
8 A Gonzalez (Spa) Kelme-Costa Blanca same time
9 A Casero (Spa) Team Coast at 1.26
10 F Casagrande (Ita) Fassa Bortolo at 1.31

General classification

1 R Heras (Spa) US Postal Service 66hrs 58mins 9secs
2 A Gonzalez (Spa) Kelme-Costa Blanca at 1min 12secs
3 O Sevilla (Spa) Kelme-Costa Blanca at 1.45
4 J Beloki (Spa) ONCE-Eroski at 2.09
5 I Mayo (Spa) Euskaltel-Euskadi at 4.15
6 F Garcia Casas (Spa) Bigmat.Auber 93 at 4.36
7 F Casagrande (Ita) Fassa Bortolo at 4.48
8 G Simoni (Ita) Saeco-Longoni Sport at 6.04
9 A Casero (Spa) Team Coast at 6.18
10 M Beltran (Spa) Team Coast at 7.00