Mark Cavendish has admitted he does not know how his training for the Olympics will affect his Tour de France hopes.
"I really don't know how it will be," said the 31-year-old, who has won 26 Tour stages but is yet to win an Olympic medal.
"It could be the best thing I've done, it could be the worst thing I've done."
The Isle of Man rider is third on the all-time Tour stage wins list, two behind France's Bernard Hinault and Belgium's Eddy Merckx, who has 34 stage victories.
Cavendish has never worn the race leader's yellow jersey, something he would achieve if he won Saturday's opening stage, however he insists it has never been "a career target, it is just something I haven't done".
However, he played down talk of leaving the race early to focus on his Olympic ambitions.
"I'm not coming to the Tour de France planning to stop," he said. "This is my 10th Tour de France. Every time I stopped, it's been for different circumstances.
"I was in bed for a week after the Tour de France last year. I got sick. I know I can't afford to do that this year.
"The biggest stage in the world is the Champs-Elysees for a sprinter. I know that my eight team-mates are going to do their best to get to Paris and I'm going to try to do my best to get to Paris."
Meanwhile, defending champion Chris Froome, who is also in the Great Britain cycling squad for Rio, but will compete in the road and time trial race races, is aiming for his third Tour de France win in four years.
He changed his early season schedule in an effort to peak for the Tour and hold his form for Rio.
"In previous seasons I'd been in that shape and then basically tried to hang on to it whereas now I feel as if I've only just got there," the Team Sky rider said.
"Hopefully it means that because we've delayed everything I'll be able to hang on to it a bit longer, and hopefully into Rio too."
The three-week 21-stage race begins in Normandy on Saturday with a race from Mont Saint-Michel to Utah Beach. The race visits the Pyrenees mountains before heading across to the Alps and finishing in Paris on Sunday, 24 July.