Home favourite Vincenzo Nibali strengthened his grip on the Giro d'Italia race lead with a commanding victory in the stage 18 mountain time-trial in the Dolomites today.

Nibali (Astana), who was third behind Sir Bradley Wiggins at last summer's Tour de France, won the 20.6-kilometre race against the clock from Mori to Polsa by 58 seconds from Samuel Sanchez (Euskatel Euskadi) to enhance his hold on the pink jersey.

Second-placed Cadel Evans (BMC Racing) conceded two minutes 36 seconds after finishing 25th on the stage to fall back to more than four minutes behind with three days of racing remaining.

Rigoberto Uran (Team Sky) remains third, 4mins 12secs adrift, after finishing sixth on the stage, 1:26 behind Nibali.

The race appears to be Nibali's to lose.

The 28-year-old Italian is seeking a second Grand Tour success following his victory in the 2010 Vuelta a Espana and has been in supreme form in his home race.

In teeming rain, Nibali soared up the ascent to Polsa to win in 44:29, with Sanchez almost a minute adrift. Damiano Caruso (Cannondale) was third, 1:20 behind.

Michele Scarponi (Lampre-Merida) was a second further behind in fourth and remains fourth overall, 5:14 behind Nibali ahead of tomorrow's 139km route from Ponte di Legno to Val Martello/Martelltal, the 19th stage and penultimate route in the mountains.

The race finishes on Sunday in Brescia, with a sprint finish expected which would favour Briton Mark Cavendish (Omega Pharma-QuickStep), the winner of four stages in the race so far and points classification leader.

Cavendish is aiming for a points classification clean sweep after winning the titles at the Vuelta and Tour in recent years.