A total of 21 AFC and OFC teams and Israel[1] entered the competition. However, South Vietnam could not compete after being annexed by Vietnam. The Asian zone was allocated 1 place (out of 16) in the final tournament.
Format
There would be two rounds of play:
First Round: The 21 teams would be divided into 5 groups. The groups had different rules, as follows:
Group 1 had 6 teams. The teams played against each other once in Singapore. The top 2 teams after the group matches played against each other in a single match. The winner would advance to the Final Round.
Groups 2 and 3 had 4 teams each. The teams played against each other on a home-and-away basis. The group winners would qualify.
Group 4 had 4 teams. The teams played against each other twice in Qatar. The group winner would qualify.
Group 5 had 3 teams. The teams played against each other on a home-and-away basis. The group winner would qualify.
Final Round: The 5 teams played against each other on a home-and-away basis. The group winner would qualify.