Argentina moved closer to joining an expanded southern hemipshere rugby competition after the game's governing body (IRB) approved $10 million in funding, but New Zealand rugby chief Steve Tew said player eligibility remains an issue.

Last week, the IRB approved $10 million in funding for the Tri-Nations governing body SANZAR (South Africa New Zealand Australia Rugby) to cover any shortfall from the Pumas joining the competition.

New Zealand Rugby Union (NZRU) Chief Executive Tew told Reuters that while funding had been one of the sticking points for SANZAR, player eligibility was a bigger concern.

A 'Four Nations' tournament, following an expanded Super 15 club rugby competition, would not start until late August.

Many Argentine players are contracted to clubs in Europe, where the seasons begin around the same time.

"The funding from the IRB is an important part of the conditions that we set," Tew said at the launch of ticket sales for next year's rugby World Cup.

"But the most important is the guarantee that we can get the Argentine players from their clubs to play during this window.

"We understand the IRB executive committee have made a recommendation to go to council in May to have the regulation, called regulation nine, extended to cover a Four Nations window.

"If that happens then SANZAR will be a lot more confident that Argentina will be able to play a part in the tournament and we will be in a better position to make a decision."