England and France are being targeted to play in the southern hemisphere's Tri-Nations series.
Australian Rugby Union managing director John O'Neill is keen for the two countries to join the annual event.
O'Neill believes the addition of the top two northern hemisphere sides would increase interest among television viewers.
Current Six Nations title holders England and World Cup finalists France would join Australia, New Zealand and South Africa in the annual tournament, played on a home-and-away basis.
O'Neill said: "The possibility always exists for the Tri-Nations to turn into a Five Nations tournament.
"France and England would obviously be the two major contenders.
"It is great when you have the British Lions around, like this season, but that only comes along once every 12 years.
"I think the SANZAR countries, in the light of changes all around the world, have to test some models, go to the broadcasters, and say 'what do you think of this?"'
O'Neill's view is also shared by former South Africa coach Nick Mallett.
He said: "A competition involving the SANZAR teams, England and France would be quite something and might improve on the repetitiveness of the Tri-Nations.
"I've no doubt that England and France are right up there with the southern hemisphere SANZAR teams".
However, Mallett was less complimentary about the remaining Six Nations sides.
He added: "Wales, Scotland, Ireland and little Italy are somewhere behind, with no more than a 20 per cent chance of winning against the top five".
O'Neill would also like to see the Super 12 competition expanded to a global event comprising 20 teams.