Romain Bardet was victorious on stage 18 of the Tour de France as Chris Froome maintained his commanding advantage to move a step closer to a second title in Paris on Sunday.

Bardet (Ag2r La Mondiale) was fourth in the 2014 Tour and 11th overall at the start of the day and broke clear from the breakaway to triumph in Thursday's 186.5-kilometres route from Gap to Saint-Jean-de-Maurienne.

Froome's challengers for the yellow jersey were unable to reduce his significant advantage as the Team Sky leader finished 12th, three minutes and two seconds behind Bardet.

Nicolas Roche was 40th, 15'41 behind Bardet, with Dan Martin one minute and 40 seconds behind his cousin in 46th. Roche lies 32nd in the general classification while Martin is 44th.

30-year-old Kenya-born Briton Froome leads Nairo Quintana (Movistar) by 3mins 10secs and his rivals are running out of opportunities.

Colombian climber Quintana seems most likely to challenge Froome, but just two stages in the Alps remain before Sunday's ceremonial finish on the Champs-Elysees.

Froome will be keen to make an impression on both Friday and Saturday as the finishes hold mixed memories.

He controversially attacked Team Sky leader Bradley Wiggins in the 2012 Tour stage to La Toussuire, which hosts Friday's finish, and in winning the 2013 title he struggled up Alpe-d'Huez.

Alpe-d'Huez, with its 21 hairpin bends, is a fabled ascent and Froome would dearly love to win there in the yellow jersey to cement a second Tour title.

His team-mate Geraint Thomas (Team Sky) remains fourth, but the Welshman's priority is to help Froome's bid for glory.

When Alejandro Valverde (Movistar) lost contact on the Col du Glandon it looked like it could be a better day for Thomas, but the Spaniard fought back to remain third, 4:09 adrift.

Fifth-placed Alberto Contador (Tinkoff-Saxo) made a short-lived attack on the Col du Glandon, but was swiftly reeled in and he remained fifth, 6:40 adrift.

Twenty-nine riders formed the day's early breakaway, including Joaquim Rodriguez (Katusha), who took enough King of the Mountains points on the day to seize the polka dot jersey from Froome.

The Spaniard had been wearing it due to being second in the classification and took his chance on an undulating day featuring seven categorised climbs.

Froome, in the yellow jersey, had greater concerns than polka dot points and was expecting his rivals for the maillot jaune to launch early attacks.

It was Contador who blinked first, attacking 8km from the summit of the day's sixth categorised climb, the hors categorie (beyond category) Col du Glandon.

Team Sky did not follow and allowed defending champion Vincenzo Nibali (Astana) to escape too, but they reacted when Valverde and Quintana accelerated.

Quintana made some gains going over the summit, but Thomas reeled him in and the group caught Contador on the descent.

Valverde also rejoined the bunch on the downhill, prior to the picturesque ascent of the 3.4km Lacets de Montvernier, with its 18 hairpin bends.

Up ahead Bardet attacked alone and had a 40-second advantage at the foot of the final climb, with Pierre Rolland (Europcar) among those chasing.

It was a lead Bardet would not relinquish as he secured France's second win of the race, after team-mate Alexis Vuillermoz's win on stage eight.

Behind Bardet, Froome had three team-mates for company - Thomas, Nicolas Roche and Leopold Konig.

Contador followed team-mate Rafal Majka and Quintana went too on the final climb, but Team Sky shadowed the move to get through the stage unscathed and one day closer to Paris.