Casey Stoner has led a number of riders vowing not to race at the Japanese Grand Prix this year over fears that radiation levels at the Motegi circuit may not be safe.
The Motegi race had been scheduled to take place on April 24, but was postponed to October 2 in the wake of the devastating earthquake and tsunami that hit the country earlier this year.
The damage caused included a radiation leak at a nuclear power station in Fukushima, around 110 miles from the circuit that is owned by Stoner's employer Honda. Japanese authorities insist that the area is safe.
While the likes of Jorge Lorenzo and Valentino Rossi previously voiced their concerns about going to Japan during the Catalan Grand Prix weekend in June, Stoner is the first rider to categorically state that he will not compete.
"I won't go," said the Honda rider, who currently leads the World Championship.
"My opinion I have had for some time, not as long as Jorge, but I took some time to make my decision and I will not go there. I am sure most riders are of the same opinion. That's my decision and I guess it is up to the organisers to figure out what is going to happen."
"We have already discussed it (with the Honda team), but not thoroughly because people are waiting on different things. They know my position now and whether they think I am going to change my mind, I don't know. It's something we have to make very clear very soon.
"If there is no race there, there can't be a penalty but I'm not going regardless of anything, I have already made up my mind. This doesn't mean we aren't supporting Japan."
His Honda team-mate Dani Pedrosa said that the situation was being discussed by the riders behind closed doors.
"The situation is not clear but most riders do not want to go so we are considering what possibilities we can do," he said.
Lorenzo, who said at Barcelona in June that he was not convinced about the safety at Motegi, and that he did not trust safety information given out by governments, said that his mind has not been changed.
"This is a decision from a long time ago and I have the same position," he said. "So I am not active in the [ongoing discussions] about going to Japan because I have already made my decision."