FIFA had previously indicated that the 2026 finals, which will expand to 48 teams from 32, would see countries divided into 16 groups of three during the first round.
Under that format, the top two teams in each group would advance to a 32-team knockout tournament.
However, FIFA president Infantino said the thrilling success of the existing first-round format at the Qatar World Cup -- where teams were divided into traditional groups of four -- had prompted a rethink.
Several groups in Qatar went down to the wire, with qualification hanging in the balance until the final whistle.
"The groups of four have been absolutely incredible until the last minute of the last match," Infantino told a press conference in Doha.
"We have to revisit or at least rediscuss the format, whether it's 16 groups of three or 12 groups of four. This is something that will be on the agenda in the next few weeks."
Infantino added that the World Cup format for 2026 could be modelled along the lines of the European Championship, which has six groups of four, with the four best third-placed teams also advancing to the knockout rounds.
The 2026 World Cup is being co-hosted by the United States, Canada and Mexico.
Infantino said the enlarged competition would lead to a financial bonanza for FIFA.
Revenues in the four-year cycle leading up to 2026 are projected to increase to $11 billion -- up from $7.5 billion in the cycle ending in 2022.
Asked to explain the huge projected increase in revenues, Infantino cited the expanded number of teams, existing stadium infrastructure and the size of the North American market.
"We are bullish about the power of football," Infantino said. "We are convinced the impact of the game will be massive.
"It has been massive here and it will be incredible in North America. Three huge countries, 48 teams.
"More games, revenues will go up in terms of broadcasting, in terms of sponsorship, hospitality.
"We will play in huge stadiums used for American football, 80-90,000 capacity. We are expecting 5.5 million fans travelling for these events."
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