The Australian Rugby Union (ARU) is supporting a call by its New Zealand counterpart for changes to the World Cup cost structure.
The New Zealand Rugby Union says this year's tournament will leave it about $13 million out of pocket, and the loss could force it to withdraw from the 2015 World Cup as a last resort.
ARU chief executive John O'Neill says the Rugby World Cup economic model is unsustainable and unacceptable.
Mr O'Neill says the 10 tier-one unions have collectively lost about $100 million this year due to the tournament's impact on the international match schedule.
NZRU chief executive Steve Tew on Wednesday warned that the International Rugby Board (IRB) needed to urgently undertake a major shake-up of the tournament if it wants the All Blacks to show up in four years' time.
He is asking the IRB to, among other things, loosen the strict rules that shut out the All Blacks' sponsors during the Cup, change the event's date and pay the unions more money from its profits.
The IRB has said it decided in May that it would review the tournament's commercial arrangements after the 2011 event.