CASEY STONER has been diagnosed with mild anaemia after the Australian underwent medical testing in the United States to determine the cause of his recent bouts of illness and exhaustion.

The 2007 MotoGP World Champion has struggled with his physical fitness since the Catalunya Grand Prix, when a visibly exhausted Stoner struggled to dismount his motorcycle after fading in the latter stages of the race in Barcelona.

The Ducati rider again displayed signs he wasn’t well during the US Grand Prix at Laguna Seca, prompting Stoner to remain in the US to undergo an examination and find a solution to his woes.

Stoner said he will commence the necessary treatment to return to full fitness and reignite his charge for a second title.

“I’ll be in the US until Saturday to do all the tests,” Stoner said.

“Hopefully step by step I will feel better with their indications. I still don’t feel like I am 100 percent, but the biggest problem now is the ribs that are very painful after the crash in the USA GP qualifying.

“It will be probably another hard weekend, but as always, we will do our best to stay as much as possible close to the lead of the championship.”

Meanwhile, Yamaha has denied claims the team refused to hire Stoner for the 2007 season at the request of Italian superstar Valentino Rossi.

It has long been rumoured Rossi’s dislike for Stoner scuppered attempts by the Japanese manufacturer to sign the former Honda satellite rider as a teammate for the eight-time World Champion.

Yamaha team boss Masao Furusawa told gpweek.com: “He has never said “I hate some guy,” or “I don’t want to invite some rider.” That is a decision for Yamaha, and Valentino at this point is really a gentleman.

“In the usual conversations, of course he shows his preferences. He likes Colin (Edwards) very much, he likes Nicky Hayden. Maybe he hates Casey Stoner. I don’t know. But he never said anything like that.”