Argentina have been invited to join South Africa, New Zealand and Australia in an expanded southern hemisphere championship from 2012.

The Tri-Nations governing body SANZAR announced yesterday they had extended a conditional invitation to the Pumas to join them in an annual four-nations tournament after their breakthrough performance at the last World Cup.

"To have the Pumas, third at Rugby World Cup 2007 and currently ranked sixth in the world, join with the three top ranked international teams in world rugby will be exciting for fans, players, sponsors and broadcasters across our four countries and beyond," SANZAR chief executive Andy Marinos said in a statement.

"They play a different style to the All Blacks, Springboks and Wallabies and their inclusion will see the Tri-Nations evolve to be a truly southern hemisphere championship."

Although the invitation is only conditional and still has to be approved by SANZAR's broadcasters, Argentina Rugby (UAR) president Porfirio Carreras welcomed the news.

"This is a momentous time for rugby in Argentina and I would like to thank my board and everyone who supported us to reach this point," he said.

The Pumas have been pushing for inclusion in the southern hemisphere's major tournaments since they finished third at the 2007 World Cup, ahead of New Zealand and Australia, despite not being part of a regular international competition.

They were overlooked for inclusion in the southern hemisphere's Super provincial competition, which will be increased from 14 to 15 teams from 2011, but SANZAR officials left open the door for possible inclusion in the Tri-Nations.

They have also promised to offer places to the top Argentine players, who usually ply their trade in the rich European club competitions, in the Super 15.

Under the proposed format for the Four Nations, each team would play each other home and away, giving all countries six games and a total of 12 matches overall.