FIFA president Gianni Infantino said proposals for a 32, 40 or 48-team World Cup in 2026 were still on the table and that a larger tournament would not mean a drop in quality.
He also stood by his own idea, first mooted last week, for a 48-team tournament, starting with a playoff round featuring 32 teams in which the 16 losers would go straight home after a single game.
A document presented to the FIFA Council, and seen by Reuters, offered 10 different possible formats, for varying numbers of teams.
"There is a positive feeling around the council but the details are still to be elaborated, whether it's 40 teams, eight groups of five or 10 groups of four, or 48 teams with a playoff at the start," Infantino told reporters. "This is still very much a work in progress."
Infantino said the standard of the tournament would not be affected by having more teams.
"I don't agree with diluting the quality," he said. "I would like to remind everyone that in the last World Cup, Italy and England were eliminated by Costa Rica."
Infantino's own suggestion, made during a presentation in Bogota last week, was for a playoff round featuring 32 teams, where the losers would go home and the winners would proceed to the group stage, joining 16 teams who would receive a bye.
Critics have questioned whether it would be viable for teams to spend weeks preparing for the tournament and then to travel around the world for a single game, but Infantino said it was.
"Already today, you have playoffs where teams travel from one part of the world to the next and they play home and away in four days," he said, adding that the playoff would be a "final" for the teams involved.
"It's certainly an exciting moment for the country and the fans... Look at England, where one of the most followed matches is the promotion playoff (from the second tier Championship)."
Infantino also said that FIFA would take more control over ticketing and organisation at the World Cup from 2022 onwards as part of its strategy for the future.
He said this was a question of streamlining the administration and did not stem from a lack of trust in local organisers.
"It has nothing to do with trust, it is just to do with efficiency," he said. "It's simply about being professional."