The IRB are urging SANZAR to pick a Japanese team as their 18th Super Rugby team when the competition expands in 2016.
Japan will host the 2019 Rugby World Cup and the IRB believe that adding a Japanese team to Super Rugby will help create momentum for their showpiece event.
There are currently 15 Super Rugby teams and they will be joined by a team from Argentina and a sixth South African team. The 18th team is expected to come from Asia.
IRB chief executive Brett Gosper says that they would prefer the 18th Super Rugby team be a Japanese one instead of Singapore who are understood to be considering a bid.
"The IRB, given there is a World Cup in Japan in 2019, we would be very happy with any part of Asia," Gosper told The Australian.
"Certainly anything that continues to gain momentum in Japan would be ­appealing for us.
"Our preference is they choose something that makes it work for the competition obviously, but ­anecdotally, Japan would be interesting for us.
"It may provide other challenges from a logistics point of view. Flights from South Africa and so on might not be the simplest option, but look at it from a purely selfish IRB stand, Japan would be interesting.
"It is a strong market. It would create greater interest in the World Cup. It would build the competitiveness of some of the Japanese players who were in that team.
"It would provide interest for the fan base there. It would be good momentum towards the World Cup and eventually the Olympics where sevens will be played next time after Rio."
Gosper added that it was unlikely that a combined Pacific Islands team would join Super Rugby.
"There is a model that adds cost and there is a model that may add revenue when you select teams in SANZAR. They have to make those calls," Gosper said.
"There are commercial cost imperatives they've got to consider. It's not out of the question if someone sets it up in a way that is viable. "
"It is possible, but it is not looking likely at the moment."