Armstrong should suffer for his lies: Djokovic

World tennis number one Novak Djokovic delivered a scathing verdict on Lance Armstrong's confession that he used performance-enhancing drugs, saying the American was a disgrace to cycling and should "suffer for his lies".

Armstrong brought an end to years of denial on Thursday by admitting to Oprah Winfrey in a televised interview that he had cheated his way to a record seven Tour de France titles.

"I think it's a disgrace for the sport to have an athlete like this," Djokovic said.

"He cheated the sport. He cheated many people around the world with his career, with his life story.

"It's just not the way to be successful. So I think he should suffer for his lies all these years. I lost a lot of faith in cycling. I used to watch it. There has been so much controversy about that sport."

Djokovic, who beat Radek Stepanek 6-4, 6-3, 7-5 on Friday to advance to the Australian Open fourth round, was happy for tennis officials to increase the number of blood tests, which are able to detect a wider range of banned substances.

He had last been blood tested about six or seven months ago.

"It was more regularly in two, three years ago," Djokovic said. "I don't know the reason why they stopped it.

"From my point, I mean, I was more than clear. I have nothing against the blood tests ... even though I prefer urine more. I don't like the needles too much.

"But of course the money in that direction should be invested because it's always, let's say, a safeguard for our sport that they're investing money in our sport that is going to protect our sport and players."

Djokovic added he felt that tennis was one of the cleanest sports in the world but he would have no problem being tested more.

"I have nothing against the anti-doping federation testing me 10, 20, 30 times a year.

"I think as long as I know as many numbers of testing for the other players, I'll be happy. So as long as we keep it that way, I have no complaints about testing."