Lopez, riding for Astana, arrived alone at the 2,510 metres summit of the Alto Hoya de la Mora after overtaking Briton Adam Yates in the final kilometres.

Froome, seeking to become only the third rider to win the Tour de France and Vuelta in the same year, countered the move by his closest rival, Vincenzo Nibali of Italy, on the final climb and widened his advantage over him by six seconds.

He now leads the Italian Bahrain-Merida rider by one minute and one second.

Russia's Ilnur Zakarin moved up to third overall by finishing second behind Lopez, 36 seconds off the pace, with Wilco Kelderman third on the 129.4km ride from Alcala la Real.

Froome, once again helped to a strong finish by Team Sky team-mates Wout Poels and Mikel Nieve, finished fifth, with Nibali seventh.

An exhausted Yates, who is yet to win a stage at a Grand Tour, was caught in the final 4km, almost coming to a halt as Lopez raced past him.

It was Lopez's second stage victory of this year's race, having also won stage 11, and he now moves up to sixth overall, two minutes and 51 seconds behind Froome.

The 23-year-old's supposed team leader, Fabio Aru, dropped to seventh as the Italian lost more time on those around him.

Tomorrow is a rest day, and racing resumes on Tuesday (September 5) with a 40.2km time trial from Circuito de Navarra to Logrono.

There are five more stages after that, with the race due to finish in Madrid next Sunday (September 10).