Former MotoGP champion Valentino Rossi has admitted he may not travel to the Japanese Grand Prix in October because of health fears in the country.
Japan was hit by an earthquake, tsunami and nuclear emergency in March, but the race was rescheduled for 2 October.
"I really don't think I'll go to Japan," 32-year-old Rossi said.
"I was hoping the championship organisers would make the right decision, but that hasn't been the case and now we've got a serious problem."
The Japanese Grand Prix was originally scheduled for 24 April but following the disaster organisers insisted it would still take place later in the year.
Several riders, including Jorge Lorenzo and Casey Stoner, have said they do not intend to compete - though Stoner admitted before winning last Sunday's Czech Republic Grand Prix that he may change his mind.
British rider Cal Crutchlow and his Tech 3 Yamaha team have already confirmed they will race.
The race is scheduled for Motegi, which lies north of Tokyo but several hundred kilometers south of the worst-affected radiation zones in north-eastern Japan.
The March earthquake and tsunami left more than 20,000 people dead or missing and also touched off a nuclear crisis.