JRFUchairman Nobby Mashimo said Singapore and Hong Kong could still host matches but only if it made financial sense.
"We are not going to say it's not an option," Mashimo said. "Of course you have to wonder if there's a handicap for teams involved.
"The conclusion might be that a seven-hour flight to Singapore or four hours to Hong Kong is unfair. But we also have to weigh up the overall strategic factors.
"The decision will be made with input from the IRB but we need to look at how it would help ticket sales.
"Over the next 10 years we could see China's rugby market rise if rugby sevens is approved for inclusion in the Olympics (in 2016) -- or possibilities for South Korea."
"We will have to see if there's a business advantage to it before making a decision," he added.
Japan won last month's IRB vote to host the 2019 World Cup with the 2015 tournament going to England on the recommendation of the event organisers.
The Japanese had been surprisingly beaten by New Zealand in the voting for the 2011 World Cup.
"I felt like crying when we got the 2019 World Cup," confessed Mashimo, who along with Japan coach John Kirwan was lobbying IRB members late into the night before the July 28 vote.
"Until the last minute we were worried the IRB might not follow the recommendation. When it was announced it was extremely emotional."
Mashimo said the JRFU, who will make use of stadiums constructed for the 2002 football World Cup Japan co-hosted with South Korea, were satisfied at landing the 2019 World Cup.
"We wanted 2015 but on balance maybe the World Cup had to return to Europe," he said. "
"With the economic downturn it makes sense to boost the coffers before going outside Europe again.
"I feel sorry for New Zealand having to stage the (2011) World Cup with the global recession still with us. It will be tough for them."
Mashimo admitted Japan's biggest challenge was to build a team capable of reaching the quarter-finals in 2019. The "Brave Blossoms" have won just one game in six World Cup appearances.
"Japan reached the knockout stages at the 2002 football World Cup and we need to match that," he said.
"It will be important in terms of ticket sales if we have a team capable of that. We must improve. Japan's World Cup results have been miserable."