Japanese organisers would use Tokyo's proposed 100,000 capacity Olympic stadium plus venues from the 2002 World Cup, which the country co-hosted with South Korea.
"We probably won't be able to go for 2018 and 2022 if Tokyo does not get the 2016 Olympics," Japan Football Association (JFA) vice-president Junji Ogura told Reuters in an interview.
"We have to be realistic. The 2002 World Cup was a massive boost for Japanese football but it would be very difficult to bid for it again if the Olympic bid fails."
Yokohama, venue for the 2002 World Cup final, has Japan's biggest stadium with a capacity of almost 70,000.
"We could add the extra seats where the running track is," said Ogura. "But an Olympic stadium would have more appeal for a Japanese bid and it would keep costs low, which is important."
"In Asia we also have China, Australia and Qatar who have raised their hands," said Ogura, a member of the FIFA executive committee.
"We will need to put our heads together to devise the best strategy for Asia. If an Asian country wins the right to host the 2018 World Cup then we can't bid for the next two.
"But if we're fighting among ourselves Asia won't stand a chance. UEFA will be doing everything to bring the World Cup to Europe -- the Europeans are very clever at the political negotiating."
"Maybe England are favourites," said Ogura. "They have not hosted the World Cup since 1966 and many people around the world would like to see the final played at Wembley.
"Their bid will be very strong. A European country will probably be favourite in 2018. Many of the major sponsors want the World Cup in Europe.
"Countries such as South Africa and Brazil are a long way away so they want the tournament to return to Europe on a regular basis, and FIFA knows the sponsors have to be kept happy."
