ST. ETIENNE, FRANCE, JULY 14 -- A remarkable breakaway by defending champion Greg LeMond and Dutch rider Eric Breukink in sweltering heat today turned the Tour de France upside down.

The 13th stage from Villard-de-Lans was expected to be a leisurely 92.5-mile passage from the Alps to the Massif Central over fairly undemanding terrain. But LeMond, chasing his third Tour victory, had other ideas.

Pursued by Breukink, LeMond went on the attack, leaving behind leaders Claudio Chiappucci of Italy and Ronan Pensec of France.

Chiappucci retained the yellow jersey but found his lead over Breukink slashed from 6 minutes 55 seconds to 2:02. LeMond is in third, 2:34 behind, with Pensec fourth, 4:11 back, and 1988 champion Pedro Delgado of Spain fifth, 4:39 behind.

The stage was won by Eduardo Chozas of Spain but that proved a minor detail. He was in a bunch of five, including LeMond and Breukink, who came in together in a time of 3 hours 20 minutes 12 seconds.

"Chiappucci had been following me as if he was glued to my wheel," said LeMond. "But when I attacked, he wasn't there anymore. I'm happy. After what I did, I hoped for more than 30 seconds on Delgado. I improvised my attack -- you can't plan these things."

Chiappucci, who had taken the lead in Thursday's time trial, finished the stage 4:53 behind the pack. Pensec, who started the day in second place, saw his hopes of victory evaporate when he struggled in almost eight minutes behind.

Delgado counterattacked desperately as LeMond and Breukink threatened to go well clear before limiting the damage to 30 seconds.

With an uncomfortable ride Sunday through the Massif Central and a daunting crossing of the Pyrenees to come Tuesday, Chiappucci's chances of holding off the likes of Breukink, LeMond and Delgado appear slim.

"I fell into a trap today," Chiappucci said. "Everybody was riding against me. First, Pensec attacked and I had to try to get him back, then there were all the other attacks.

"At the end of the Tour, people will look back and they will probably say that this was the toughest stage.

"I'm not ashamed at finishing so far behind LeMond. He is a great champion. But I won't say I have lost the Tour yet."

Pensec, who held the yellow jersey for two days, had his final fling in front of large crowds lining the route to celebrate the French national holiday, Bastille Day.

He stormed away on the gentle slopes of the Col d'Ardoix and gained 1:24 on Chiappucci, a margin that would have given him back the race lead.

But LeMond and a group of pursuers caught him with 28 miles to go and he could not sustain their furious pace as temperatures rose to 95 degrees.

"They attacked up the hills. They attacked down the hills. They attacked on the flats. They attacked everywhere," said Sean Kelly, a 12-time tour veteran.

Pensec, LeMond's "Z" teammate, dropped back, further solidifying LeMond's position; earlier in the week he'd said he would serve as backup to Pensec, with the goal of helping his teammate win. Since Pensec has fallen so far back, LeMond, the team captain, can channel his energies into winning.

The leg from Le Puy en Velay to Millau is next, one of two relatively flat stages before the tour heads south toward the Pyrenees. The 2,110-mile race race ends July 22 in Paris.

"Now I feel things are moving," Delgado said. "The serious part of the Tour de France is starting. We'll see what happens in the Pyrenees but I think this race will not be decided until the very end."