Astana's Vincenzo Nibali has all but sealed victory in the Giro d'Italia with a win in a snow-swept stage 20 at Tre Cime di Lavaredo.

The 28-year-old launched an attack 2.5km from the line to finish 17 seconds in front of second-placed Fabio Duarte, extending his overall lead to four minutes and 43 seconds.

Team Sky's Rigoberto Uran finished 19 second off the pace in third, but jumped ahead of Cadel Evans into second in the general classification.

He leads the Australian by just over a minute with just one stage remaining.