The Indy Racing League's scheduled date at Motegi on 19 April is the key to the planned merger between the IndyCar Series and the rival Champ Car World Series.
The IRL race in Japan clashes with the Champ Car round at Long Beach, which is one of three events that will be added to the IndyCar calendar if the proposed deal goes ahead.
The Long Beach street race date is not flexible because a contract is in place to close the roads for the event only on that specific weekend, so Motegi would have to be rescheduled.
IRL boss Tony George and series presidents Terry Angstadt and Brian Barnhart will fly to Japan tomorrow to encourage Motegi officials to move the race to another weekend.
George warned against over-optimism until all issues were resolved and a deal was completed.
"Every time we seem to get close [to a successful merger], a new obstacle gets in the way," he told American newspaper the Indianapolis Star.
Champ Car co-owner Kevin Kalkhoven agreed that there will be no progress with the amalgamation until the Motegi date is moved.
"As long as [circuit owner] Honda won't move Motegi, there won't be a merger," he told the Associated Press.
"It's a major hurdle but it's not the only one. There are significant advantages in merging but there are also significant advantages in not doing it. But at the moment there are no discussions until they move Motegi."
Kalkhoven also expressed his disappointment that details of the latest round of merger talks had been leaked to the press. Respected American journalist Robin Miller broke the story on the SpeedTV website last night.
"Once again, as has happened previously in the past four years, somebody has leaked a story to the press, and the press has turned it into a tornado," he told the Indianapolis Star.
"Now it has everyone running around in a circle. It's almost malicious, and it disappoints and infuriates me.
"We were very close to a deal a couple of years ago and everything got leaked. Then instead of the key people working it out, everybody gets involved in the discussion. If people are trying to help unification, silence is the best thing."
Senior IRL officials are currently negotiating with other circuits about adjusting their dates to accommodate Champ Car rounds at Edmonton and Surfers Paradise into the IRL season.
But George admitted that rearranging the schedule less than two months before the opening round would be a major challenge.
"You just can't go changing all the dates around when you have contracts," he told the Indianapolis Star.