Argentina are sixth in the rankings, above England, Scotland and Wales

IRB chief executive Mike Miller said Argentina could join the tournament next year if everything went to plan.

But Argentine Rugby Union president Alejandro Risley said his organisation was not looking too far ahead.

"We are looking for a regular, yearly competition but we cannot define anything if we don't have the invitation - it's too early," he said.

There's nothing to stop it happening next year if everyone wants it to IRB chief executive Mike Miller

"These comments are excellent for us, as they back an old ambition we have - this is a very important support, but unfortunately we also need the allowance from the unions who form those tournaments.

"And it is very soon to start talking about this if we don't have the invitation from the unions."

Argentina were keen to join the Six Nations but have since switched their attention to joining the southern hemisphere tournament.

The country's government has entered into discussions with its Australian counterpart to try to boost the Pumas' chances of joining the competition.

But Australian Rugby Union chief Gary Flowers has warned that Argentina's entry into the competition would require the renegotiation of television contracts signed until 2010.

"Given the Tri-Nations runs from July through to early September, and with the European season under way, that is an issue that would have to be confronted," he said.

Argentina could also face problems in terms of player availability, with virtually all of their top players based with European teams whose needs would not easily allow them to spare players for the Tri-Nations.

Nevertheless, there is backing from the IRB for Argentina to join the tournament.

"The Tri-Nations are all agreed that we need to do something about Argentina and the IRB have made it clear that we will look at any scheme that helps to ensure they are properly integrated into international rugby," said Miller.

"There's nothing to stop it happening next year if everyone wants it to."