"WADA is seeking a period of ineligibility of between one and two years," it said in a statement, after the Italian twice tested positive for the banned substance clostebol in March but was cleared to carry on playing.

The 23-year-old Sinner, who recently won the US Open for his second Grand Slam title and is currently in action in Beijing, has denied doping.

Last month, the International Tennis Integrity Agency (ITIA) said that Sinner had been cleared of any wrongdoing after twice testing positive earlier in the season.

The ITIA accepted his explanation that the drug entered his system when his physiotherapist used a spray containing it to treat a cut, then provided massage and sports therapy to the player.

WADA said in its statement that it lodged an appeal to CAS, the top court in sport, on Thursday.

"It is WADA's view that the finding of 'no fault or negligence' was not correct under the applicable rules," it said.

It added: "WADA is not seeking a disqualification of any results, save that which has already been imposed by the tribunal of first instance.

"As this matter is now pending before CAS, WADA will make no further comment at this time."

Clostebol is an anabolic agent prohibited at all times by WADA.

After winning the US Open, Sinner said that the controversy over his failed tests was still on his mind.

He defeated Taylor Fritz in straight sets to add the New York title to his Australia Open triumph in January.

"It was and it's still on my mind. It's not that it's gone, but when I'm on court, I try to focus about the game, I try to handle the situation the best possible way, communication with the team, in the practice courts," said the world number one.

"It was not easy, that's for sure, but I tried to stay focused, with which I guess I've done a great job."

The decision to clear the Italian was met with scepticism by some players in the locker room who suggested that Sinner had benefited from preferential treatment due to his status in the sport.