The FIFA Council has rubber-stamped plans to expand the World Cup to 48 teams from 2026 onwards.
FIFA president Gianni Infantino's revamp plan received unanimous backing.
Delegates in Zurich were asked to vote on four proposals to change the existing format or stick with the current format of 32 teams.
This is the first time since the 1998 World Cup that changes have been made to the make-up of the tournament, with the 2026 competition set to feature 16 groups of three.
Infantino's preferred option for change was for a 2026 competition featuring 16 groups of three, followed by a 32-team knock-out, increasing the number of games from 64 to 80 but remaining inside a 32-day schedule.
There were also options to have a 40-team tournament, with 10 groups of four or eight groups of five, but the only other 48-team make-up would see a 32-team one-game knockout round with the winners joining 16 already-qualified teams.
Infantino has also suggested that penalty shoot-outs be brought in to settle the results of all drawn games, thereby minimising the risk of teams colluding in their final group games to eliminate others from the tournament.
The Swiss has repeatedly said his main motivation for expansion is to give more nations a chance of experiencing the joy of a World Cup, which will bolster international football in developed markets and help its growth in new ones.
More details will be announced at the conclusion of Tuesday's meeting - although the allocation of the extra 16 qualification slots under the new format was not expected to be resolved at this point.
The African and Asian nations are expecting significant increases on their current allocation of four spots apiece.
The other major decision regarding 2026 - who will host the event - is not scheduled for consideration until 2020 with a bid featuring the United States, either on its own or in conjunction with one or both of Canada and Mexico, the overwhelming favourite.
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