SALON-DE-PROVENCE, France -- The 19th Stage of the Tour de France, the longest of this year's race, is underway with Chris Froome in the overall lead.

The 222.5-kilometre ride from Embrun in the Alps through Provence has three moderate climbs but should pose no major difficulties for the top riders and is likely to end with a mass sprint at the finish in Salon-de-Provence.

The last major challenge standing between Froome and a fourth Tour title is a time trial on Saturday, a discipline the Briton excels in.

He has a lead of 23 seconds over French rider Romain Bardet and 29 seconds over Rigoberto Uran of Colombia. The race ends Sunday in Paris.