CASTRES, France (AFP) -- Belgian Tom Boonen, of Quick Step, won the Tour de France 12th stage to claim his second victory of this year's race and his sixth stage overall here Friday.

Denark's Michael Rasmussen, of the Rabobank team, retained the race leader's yellow jersey after the 178.5km race from Montpellier to here. Today will feature the first big time trial of the race, a 54km race against the clock around nearby Albi. It will be then that Rasmussen, who is currently embroiled in a row over two missed doping controls prior to the Tour de France, will find out if he has a realistic chance of holding on to the yellow jersey. Spaniard Alejandro Valverde is second overall at 2min 35sec, Iban Mayo is third at 2:39 and Australian Cadel Evans is fourth at 2:41. However, a few other close contenders, including Germany's Andreas Kloden and American Levi Leipheimer will be looking to seize their chance at reducing their deficits in the general classification. With two consecutive days, of three in total, of tough climbing in the Pyrenees to follow the time trial, Friday was one of the few remaining chances for Boonen to reinforce his grip on the points classification's green jersey. However, there were a few riders hoping to spoil the former world champion's plans to add bonus points on to his tally. Frenchman Pierrick Fedrigo of Bouygues Telecom and Spaniard Amets Txurruka of Euskaltel broke free of the peloton after 57km of racing, and they managed to build a maximum lead of 11 minutes on the peloton. But in the closing stages of the race Boonen's Quick Step team, Liquigas, Lampre and Francaise des Jeux decided to work together in a bid to make sure the leading pair would not get to the finish line on their own. Their lead of five minutes as they came over the top of the day's fourth and last moderate climb soon began to be whittled down in the closing, mostly downhill 48km. Agonisingly, the pair were caught with just one kilometer to race and the finish line in sight. Boonen, who won the sixth stage of the race, came in on the wheel of his teammate Gert Steegmans, and in the closing 50 meters launched himself to the finish to beat Germany's Erik Zabel of Milram. South African Robert Hunter, who made history by winning Thursday's stage, finished third. Boonen, 26, now has six stage wins on the race -- and one hand on the green jersey