Alberto Contador fought to retain the Tour de France lead and Lance Armstrong clung to second in Tuesday's 16th stage, which was won by Spanish rider Mikel Astarloza.

Contador and Armstrong finished in a group of race leaders behind Astarloza in the 159-kilometre (99-mile) ride through the Alps from the Swiss town of Martigny to Bourg-Saint-Maurice.

Contador, the 2007 Tour winner and pre-race favourite this year, said he struggled to fight off an attack led by brothers Andy and Frank Schleck of Luxembourg in the day's second big climb.

Difficult day

"We had expected (an attack) and I gave my maximum. I could resist but not without difficulty," Contador said. "I'm happy after this difficult day."

Astarloza, a 29-year-old rider on the Euskadi Euskaltel team, thrust his fists in the air and kissed his fingers as he crossed the line in 4 hours, 14 minutes, 20 seconds - six seconds before French riders Sandy Casar and Pierrick Fedrigo.

With about 2 kilometres (1.2 miles) to go, the Spaniard escaped three other breakaway riders with him and held on through the finish to collect his first Tour stage win.

"I was lucky to leave alone and finish alone," Astarloza said. "I'm a complete rider, but I'm not good at the sprint - so I have to attack from far away.

"This is the biggest day of my career."

Contador, Armstrong, fourth-place teammate Andreas Kloeden, and third-place Bradley Wiggins of Britain all crossed 59 seconds after Astarloza.

Overall, Contador leads Armstrong by 1:37. Wiggins is third, 1:46 back, while Kloeden is 2:17 behind and Andy Schleck is fifth, trailing by 2:26.

Armstrong retained his spot only after playing catch-up.

With about 36.4 kilometres (22.6 miles) left, Andy Schleck attacked. He was quickly joined by Contador and a few other riders - but not Armstrong.

The Texan, after dropping back by a maximum of about 35 seconds, then mustered a dazzling acceleration to rejoin that small group of favourites, which included Schleck, Contador and Wiggins.