Frenchman Julian Alaphilippe kept the Tour de France's overall lead on Wednesday and said he was 'ready for the Alps' after the 200km run to Gap on stage 17, won by Italian Matteo Trentin.

Alaphilippe has four riders within two minutes 02sec of his advantage as the Tour goes into three huge Alpine stages with defending champion Geraint Thomas at 1min 35 sec behind him in one of the most open races in years.

In his yellow jersey for a 13th day, the world number one looked relaxed after the balmy run from the Camargue into the town of Gap, surrounded by the daunting mountain peaks which lie in wait for the peloton.

"It was a peaceful day, it did me good, we reserved energy in this dreadful heat," said Alaphilippe.

"I'm ready for the Alps," added the 27-year-old former soldier.

"But I need to detach myself from all this going on around me," he said.

"My legs are tired, but in my mind I have never felt better," he added.

Rivals have been predicting local hero Alaphilippe would crack under pressure since he took the overall lead but Thomas' co-captain Egan Bernal lying in fifth overall was unsure.

"We all said he'd lose the lead in the Pyrenees, but here we are with just three stages remaining and he's still there," said Team Ineos' Colombian.

"Hats off to him, he's the one in the lead and he looks strong. But at last we are in the Alps," said impressive climber Bernal, the youngest man in the race.