The Japanese round of the MotoGP world championship at Motegi next weekend has been called off due to air travel problems caused by the cloud of volcanic ash in Europe.
Circuit officials said the race has been postponed and said details of alternative dates would be announced from the start of the week.
"We have received confirmation the race will be postponed," Kazunari Kinebuchi said.
A MotoGP source said the Swiss-based governing body, the International Motorcycling Federation (FIM), plans to make a statement on Monday.
The Motorcyclenews.com website reported the race, to have been the second of the season, would be rescheduled to October 3 as round 14 of the championship before Malaysia and Australia.
The next round will now be at Spain's Jerez circuit on May 2. Italian world champion Valentino Rossi leads the standings.
While most of the freight will have been flown straight on from the season-opener in Qatar, the cloud of ash has created a no-fly zone over much of northern and central Europe and made it impossible for many team personnel to reach Japan.
Formula One teams, a majority of them British-based, and international media are already facing significant difficulties in returning from China after Sunday's Grand Prix in Shanghai.