Colombia's Egan Bernal wearing the overall leader's yellow jersey celebrates on the podium after the twentieth stage of the Tour de France cycling race on Saturday. Photo: Thibault Camus/AP

ZIPAQUIRA  Egan Bernal's childhood cycling coach Fabio Rodriguez always recognised him as a fine prospect but he never imagined his young student would one day be poised to claim victory in the greatest race of all, the Tour de France.

Rodriguez, who first met Bernal when the climbing phenomenon was just eight years old, watched the Tour's penultimate stage on Saturday with a crowd of hundreds in the town square of Zipaquira, the small city nestled in Colombia's Andes where Bernal was raised.

"I knew he was really good, talented, but I didn't know that he could be where he is now," the emotional Rodriguez said, as enthusiastic locals gathered despite an early morning chill.

"You don't ever imagine that he could become the best in the world."

Bernal is set to be the first Colombian to win the Tour, after he retained the overall lead in Saturday's 20th stage, a 59-km ride from Albertville to Val Thorens.

The 22-year-old Team Ineos rider finished fourth in the stage won by 2014 champion Vicenzo Nibali and will become the youngest Tour winner for 110 years once he has negotiated the final, largely processional stage into Paris on Sunday.

"It's as though I raised him, in the sense of preparing him to handle it, to be able to manage the physical pressure," said Rodriguez, who encouraged Bernal's father to get his son into training.

Rodriguez's current students, who arrived on their bicycles to watch, follow Bernal obsessively and had the chance to meet the cyclist when he visited in December.

Colombian riders, accustomed to the thin air and steep slopes of the Andes, have a long, proud tradition of being competitive on the Tour.

Rigoberto Uran and Nairo Quintana came in seventh and eighth on Saturday. Quintana, a Giro d'Italia and Vuelta a Espana champion, had previously finished runner-up in the Tour in 2013 and 2015.

Quintana, who used to be thought of as the Colombian most likely to make the breakthrough victory at the Tour, was greeted by thousands of cheering fans on his return to the country after his second-place finishes.

The race is just Bernal's second Grand Tour, after finishing 15th last year.

He has eclipsed team mate and defending champion Geraint Thomas, who is second overall and who raised the smiling Bernal's arm in triumph when they crossed the line together in Val Thorens.

Excitement in Zipaquira mounted as the stage drew to a close, with chants of "Egan, Egan" ringing through the square, before a burst of silver confetti rained down on the crowd.

"There's so much pride, so much emotion," said amateur cyclist and Zipaquira resident Melissa Cruz, 27, dressed for a long ride on her sleek black bicycle, which she calls 'Ramona'.

"He's a very humble person," said Cruz, who cycles hundreds of kilometres each week. "He's brought us a triumph we've never had."