Sir Bradley Wiggins finished fifth on the testing sixth stage of the Tour of California to increase his lead by an extra two seconds at the top of the general classification.

Colombian Johan Esteban Chaves attacked on the final climb to claim the stage ahead of David De La Cruz Melgarejo of Spain and American Tom Danielson, with British duo Adam Yates and Wiggins finishing fourth and fifth.

Wiggins' efforts enabled him to stretch his lead at the top of the standings to 30 seconds over nearest rival Rohan Dennis, having escaped from the Australian in the final metres of the 156.1-kilometre ride from Santa Clarita to the Mountain High summit finish.

With only two stages remaining, the 2012 Tour de France winner is now within touching distance of claiming the title.

Orica-GreenEdge rider Chaves took the honours on what was the toughest stage of the race after breaking away with four kilometres to go to finish 13 seconds clear of De La Cruz Melgarejo and 41 seconds in front of Danielson. Chaves' team-mate Yates was 53 seconds back, along with Team Sky's Wiggins.