The concept, which would add value to Tests outside the World Cup, will be discussed at two major meetings next month by leading southern hemisphere body SANZAAR in London and by World Rugby in Dublin.

The proposal is understood to include points allocated to Test matches with the top placed team from the two hemispheres meeting in a final in each non World Cup year.

All the Six Nations and Rugby Championship teams would initially be involved.

Castle compared the current situation to the years leading up to the establishment of the inaugural World Cup in 1987.

"We're at that next moment where we think there's an opportunity to review and understand what the most beneficial opportunity for World Rugby is to take the profile of the sport to the next level," Castle said on Thursday

"'Certainly a World League bringing everyone together delivers that.

"It's not simple. You've got 12 stakeholders that have incredibly different commercial arrangements, high performance requirements, governance structures to get something like that approved , so it's a very complex piece of work.

"At an idea level it's got significant support from those 12 nations, now it's the realities of whether you can deliver it from a commercial and operation perspective.

"I think it's the culmination of evolution and not revolution, so we have a great international Test match product now that allows us to pinnacle that every four years into a World Cup.

"There's been a discussion about formats, we have an outline of what we think the structure could look like as a concept but the commercial realities of pinning it all together is what gets challenging."

Australian Associated Press