The ARU said the decision was taken at a meeting of the competition's governing body SANZAR in Auckland.
A board meeting today decided the structure of the tournament would be reviewed in 2001.
"We have a successful tournament that's breaking records in Australia, New Zealand and South Africa. Our broadcasters are also happy, so there's no great momentum for change," ARU managing director John O'Neill said.
There has been media speculation about an increase in the number of teams involved, possibly bringing in teams from outside the three established countries.
O'Neill said Australian and South African delegates told the meeting any expansion must involve an additional team from each of their countries before any additions from other nations would be considered.
New Zealand has five teams in the competition, South Africa four and Australia three. It runs from the end of February to May.
The SANZAR board meeting also resolved to establish a formal process to determine the distribution of broadcasting revenues.
Australia receives 27.5 per cent of broadcast funding but wants that increased over time to an equal one-third share, it said.
A deadline of July 1, 1999, has been set for the issue to be resolved, after which it will go to arbitration.
Reuters
