MONT BLANC, FRANCE, JULY 10 -- Ronan Pensec of France celebrated his 27th birthday today by taking the overall lead of the Tour de France from Canada's Steve Bauer, who had led from the opening stage.

Thierry Claveyrolet of France won today's 73.5-mile stage, which began in Geneva and ended on Mont Blanc, Europe's highest peak.

The 10th stage was marked by three difficult climbs, including the final one to 4,600 feet. On that ascent, Pensec broke away with a small group that included 1988 winner Pedro Delgado of Spain and the 1989 winner, Greg LeMond of the United States. Bauer lost contact with the main pack.

Pensec came in 16th, trailing Claveyrolet by 2 minutes 29 seconds. Delgado was seventh, 2:10 back, and LeMond was 10th in the same time as Pensec. Bauer struggled home almost two minutes behind Pensec.

That put Pensec in the overall lead by 50 seconds over Claudio Chiappucci of Italy, with Bauer third, 1:21 behind. LeMond is eighth overall, 9:52 behind Pensec.

Bauer led by 17 seconds entering the day's competition. The Canadian had held first place over Pensec since the opening stage.

"I am not that disappointed in losing the yellow jersey," Bauer said. "I still feel good and I think I can take some time back in the Alps. You haven't heard the last from me." 10th STAGE GENEVA TO MONT BLANC (73.5 MILES)

1, Thierry Claveyrolat, RMO, France, 3 hours 24 minutes 31 seconds; 2, Uwe Ampler, PDM, West Germany, 1 minute 54 seconds behind; 3, Charly Mottet, RMO, France, same time; 4, Jose Montoya, Ryalcao, Colombia, 2:10; 5, Marino Lejarreta, ONCE, Spain, same time; 6, Eric Baoyer, Z, France, same time; 7, Pedro Delgado, Banesto, Spain, same time; 8, Guido Winterberg, Helvetia, Switzerland, 2:11 behind; 9, Roberto Conti, Ariostea, Italy, 2:24; 10, Greg LeMond, Z, Waysata, Minn., 2:29; 11, Steven Rooks, Panasonic, Netherlands, same time; 12, Miguel Indurain, Banesto, Spain, same time; 13, Raul Alcala, PDM, Mexico, same time; 14, Claude Criquielion, Lotto, Belgium, same time; 15, Sean Kelly, PDM, Ireland, same time. OTHER AMERICANS AND TEAM 7-ELEVEN

26, Andy Hampsten, 7-Eleven, Boulder, Colo., same time; 50, Steve Bauer, 7-Eleven, Canada, 4:07; 85, Dag-Otto Lauritzen, 7-Eleven, Norway, 10:07; 95, Ron Kiefel, 7-Eleven, Boulder, Colo., same time. OVERALL STANDINGS

1, Ronan Pensec, Z, France, 42 hours 46 minutes 4 seconds; 2, Claudio Chiappucci, Carrera, Italy, 50 seconds behind; 3, Steve Bauer, 7-Eleven, Canada, 1 minute, 21 seconds behind; 4, Frans Maassen, Buckler, Netherlands, 2:27 behind; 5, Raul Alcala, PDM, Mexico, 7:02; 6, Uwe Ampler, PDM, West Germany, 9:22; 7, Guido Winterberg, Helvetia, Switzerland, 9:51; 8, Greg LeMond, Z, Waysata, Minn., 9:52; 9, Sean Kelly, PDM, Ireland, 9:58; 10, Erik Breukink, PDM, Netherlands, 10:15; 11, Pello Ruiz Cabestany, ONCE, Spain, 10:18; 12, Miguel Indurain, Banesto, Spain, 10:44; 13, Gianni Bugno, Chateau D'Ax, Italy, 11:07; 14, Steven Rooks, Panasonic, Netherlands, 11:07; 15, Pedro Delgado, Banesto, Spain, 11:13.