Alberto Contador (Discovery Channel) started Thursday?s seventeenth stage to Castelsarrasin in the best young rider?s white jersey but pulled on the race leader?s yellow jersey at the finish after the exclusion of Michael Rasmussen by his Rabobank team on Wednesday night.

In his first ever press conference as leader of the Tour de France, the 24 year-old Spaniard immediately faced some tough questions about doping. The most direct was if he is clean, if he has ever missed any test and about his involvement in Operacion Puerto.

?I?m clean or I wouldn?t be here,? he claimed.

?I?ve done all doping test in the race and out of the race. I?m not involved in Operacion Puerto. I was only the wrong team at the wrong moment.?

Do you work with Dr Ferrari? If not who is your coach or doctor?

?I?ve never physically met Dr Ferrari and don?t work with him. My doctors are the team doctors and I only work with them.?

What do you think about facing questions like this?

?I think it?s very sad because I really like this sport and as we?ve seen in the last few days, there are thousands of supporters along the road side in these days. It?s difficult to face these types of questions all time.?

Was it right to exclude Rasmussen?

?I don?t know if right or wrong. I don?t know enough about it all. His team decided and so I can?t say anything about it.?

Responding to easier questions Contador admitted that it was an emotional moment when he pulled on the yellow jersey and promised he will do everything he can in Saturday?s time trial to keep it all the way to Paris.

?Last night I knew it?d be a very difficult day. I was very surprised about what happened but very happy to get the yellow jersey. Yesterday I attacked a lot until last kilometre and I think I raced well. It?s not the best way to get the yellow jersey but if there?s a crash you get the yellow jersey so these things happen.?

?If 1-53 on Evans is enough to win the Tour de France depends a lot on the day. 55km is a long way and it?ll be difficult to keep the yellow jersey but I?ve got a chance in the other time trial and I?m going to do everything I can to keep it.?