The Tour de France enters the Pyrenees for 4 punishing days that will shake up the race

Tour de France cyclists set off on mountain test

REVEL, France — The 175 riders remaining in the Tour de France have embarked on the first of four punishing days in the Pyrenees that will be crucial to the outcome of the race.

Andy Schleck of Luxembourg holds the leader’s yellow jersey with a 31-second advantage over defending champion Alberto Contador, with another Spaniard — Samuel Sanchez — third, 2.45 off the lead.

Sunday’s 114.7-mile 14th stage from Revel to an uphill finish at the ski resort of Ax-3 Domaines will lead riders up two extreme climbs, including the Port de Pailheres — a long and steep ascent that is among the most difficult in cycling.

THIS IS A BREAKING NEWS UPDATE. Check back soon for further information. AP’s earlier story is below.

REVEL, France (AP) — The Tour de France was to begin one of the most punishing sequences of stages in its recent history Sunday as the riders entered the Pyrenees for four days that include two ascents of the Col du Tourmalet.

Andy Schleck of Luxembourg held the yellow jersey with a 31-second lead over the defending champion, Spaniard Alberto Contador. But that will be challenged throughout the final week of racing as the riders test their endurance and desire against some of the most difficult cycling roads in the world.

The 114.7-mile ride from Revel to the ski resort of Ax-3 Domaines on Sunday will lead riders up two extreme climbs, including the Port de Pailheres, a climb so long and steep that cycling’s governing body doesn’t even classify it, to an uphill finish.

That’s followed by two more tough stages in the mountains along the French-Spanish border, including a first climb of the Tourmalet. Then, after a much-needed rest day, on Thursday the riders turn around and cross the mountains in the other direction, to end at the top of the Tourmalet.

Though the mountains may not decide this year’s race — there is still a time-trial to come next Saturday — it is certain to end many riders’ hopes.

Schleck said he was looking forward to the competition with Contador.

“I respect him as a rider and admire him as a great person,” he said. “I’m a bit nervous for tomorrow. I’m comfortable, but I’m nervous — and I think he is, too.”

The mountains will also decide the winner of the polka-dot jersey that designates the best climber, or King of the Mountains. The jersey is being worn by Anthony Charteau of France, but as the bigger climbs offer more points, the competition is far from decided.

Meanwhile, the race for the green jersey for best sprinter will be put on hold over the mountains as the riders in contention for it struggle just to avoid expulsion for being too slow. Alessandro Petacchi of Italy holds the jersey by just two points over Norway’s Thor Hushovd.

Mark Cavendish of Britain, who won six stages last year and has taken three so far this year, is in third. Cavendish also won the sprint in Saturday’s 13th stage — but that only gave him second place in the race, as the pack couldn’t catch Alexandre Vinokourov of Kazakhstan, who finished 13 seconds ahead of everyone else for his first victory in the race since he was excluded from the Tour and given a two-year doping ban in 2007.

Seven-time champion Lance Armstrong lost more time in Saturday’s stage and is more than 25 minutes behind Schleck. He has acknowledged that he now has no chance for an overall victory. In response to a Twitter post that suggested Armstrong was planning a surprise for Sunday’s stage, he responded, “I like the sound of it.”