World Rugby has demanded Japan send a new proposal for its 2019 World Cup venues and provide assurances about the tournament's "financial security" after Tokyo's National Stadium was scrapped as the centrepiece venue.
A refurbished National Stadium was to stage the opening match, the final and other key games but those plans were scuttled last month when Japan's Prime Minister Shinzo Abe ordered the project halted over rising costs.
World Rugby said it had set out "a revised roadmap" for organisers to follow in delivering the tournament.
"World Rugby is seeking formal reassurance regarding the following key hosting criteria by the end of September in order to undertake a thorough review and analysis of the information," the governing body said in a statement.
"A revised detailed host venue proposal that delivers exceptional team and fan experience, maximising opportunities for fans to be a part of rugby's showcase event.
"A revised tournament budget with appropriate financial security."
World Rugby added that the loss of the National Stadium would have a "significant impact on the overall ticketing capacity and tournament budget".
"These are critical to an event that is the lifeblood of the game, underpinning its growth worldwide and the financial support of 120 national rugby federations."
Japanese rugby has been under fire in recent weeks, with the World Cup setback adding to concerns about the country's ability to field a Super Rugby team in next year's competition.
Japan beat out a rival bid from Singapore to add a franchise to the expanded 18-team southern hemisphere tournament but has yet to provide a name for the team or find a coach.
The franchise has only signed a handful of players, according to local media reports, with the start of the 2016 season only months away.