SANTUARIO DEL ACEBO – Primoz Roglic maintained his lead over Alejandro Valverde in the Vuelta a Espana after stage 15 on Sunday but both widened the gap between the rest of their rivals in the general classification.
Roglic's Jumbo-Visma team mate Sepp Kuss took the stage win.
United States rider Kuss attacked on the last of the four first category climbs with six kilometres remaining of the punishing 154.4 km mountain stage from Tineo to Santuario del Acebo in Asturias to catch up with lone leader Sergio Samitier.
Kuss, 24, held his own on the summit finish, coming over the line 39 seconds ahead of second-placed Ruben Guerreiro to earn his first Grand Tour stage win, while Tao Geoghegan Hart of Team Ineos came third, 40 seconds behind.
Valverde launched an attack on Roglic shortly afterwards in a bid to reduce his overall deficit although the Slovenian was up for the fight and the pair stayed together to come eighth and ninth respectively, two minutes 14 seconds down on Kuss.
The Vuelta now looks to be a two-horse race between Roglic and Valverde as they caused significant damage to the other contenders, especially 2016 winner Nairo Quintana, who finished three minutes, 50 seconds behind Kuss.
The Colombian now trails Roglic by five minutes, nine seconds with only one mountain stage remaining. His compatriot Miguel Angel Lopez also saw his hopes of an overall win fade as he lost 41 seconds on Roglic.
Lopez came over the finish line at the same time as Tadej Pogacar, who remains third overall but fell three minutes and 42 seconds behind Roglic.
Monday's stage is a 144.4 km ride from Pravia to Alto de La Cubilla. Lena, another punishing mountain stage before Tuesday's rest day. The race concludes next Sunday in Madrid.