The 2008 Rugby League World Cup in Australasia will feature 10 nations.
Australia cruised to victory in the 2000 World Cup
Australia, New Zealand, England, France and Papua New Guinea are expected to receive direct entry but other nations are likely to have to qualify.
The tournament will be the sport's first since the underwhelming event in the UK in 2000 which had 16 countries.
"We believe the 10-team format will ensure a successful tournament," said Rugby League International Federation (RLIF) chairman Colin Love.
"It will be hugely entertaining and have global benefits for the sport."
Australia won the 2000 World Cup at a canter, with numerous mismatches - including the Kangaroos' 110-4 win over Russia - undermining the credibility of the tournament.
The 1995 Centenary World Cup, regarded as a far more competitive competition, featured 10 teams.
Details of which teams will have to qualify will be finalised in March 2006.
"The qualifying groups and matches will also be structured so they function as a clear pathway for developing nations to win the right to compete with the sport's established international teams as well," added Love.
The RLIF also agreed rules regarding the make-up of each country's squad to avoid a repeat of the situation in 2000 when Lebanon fielded a team comprised entirely of Australian-based players.
The new rules require every squad to contain at least six players who have either played in the relevant domestic competition for at least one year, or who have played in one of that nation's junior international teams in the 18 months prior to the tournament.
Meanwhile, New Zealand are expected to host three of the pool matches in the 2006 Tri-Nations series between Australia, New Zealand and Great Britain.