MELBOURNE • Sanzar, the ruling body of Southern hemisphere rugby, has written to the Japan Rugby Football Union seeking clarity about the players signed to the country's new Super Rugby franchise.
This comes amid concerns about the team's participation in the provincial competition.
Japan beat off a bid from Singapore to enter a team into the expanded 18-side tournament next year but there were doubts on the side's ability to compete.
JRFU general secretary Noriyuki Sakamoto shot down media reports over the weekend that only a handful of players had been signed, saying the team had already met the 25-man quota.
However Brendan Morris, acting chief executive of Sanzar, Super Rugby's governing body, said he had asked for more details.
"We're proposing they compete in the toughest rugby competition in the world so I've written to them asking for clarification of who they've signed," he told The Australian newspaper.
With just six months to go before the start of the new Super Rugby season, Japan have yet to name a coach or even pick a name for their new team.
Sakamoto told Kyodo News that the search for a coach had been delayed by the need to find a new national coach, with Eddie Jones stepping down after the World Cup.
Jones, 55, will also quit as the director of rugby of their Super Rugby side, who are set to host three of their home matches at the Singapore Sports Hub next year.
Japan's preparations for the 2019 World Cup were dealt a blow last month when Prime Minister Shinzo Abe ordered plans for Tokyo's National Stadium re-drawn, robbing the tournament of its centrepiece venue.
Japan's National Stadium, which is being re-built for the 2020 Olympic Games, was to host the World Cup final and key games but will no longer be finished in time.
World Rugby last week demanded Japan submit a new venues plan and an updated budget by this month to provide assurances that the tournament would go ahead.
Former Australian Rugby Union chief John O'Neill fears the "ultimatum" could be a precursor to strip the tournament from Japan.
"There has been some sentiment out of the UK, in particular, that the decision to award Japan the hosting rights was one that some would like to reverse," he said.