According to the 46-year-old Italian, 16 countries would be eliminated after a preliminary knockout round.
The rest of the tournament would then be the same as it is now, with 32 teams competing in the group stages, followed by further knockout rounds.
Infantino said a decision on possible expansion would be taken in January.
“These are ideas to find the best solution,” he said. “We will debate them this month and we will decide everything by 2017.”
Infantino took charge of world football’s governing body in February.
One of his election promises was to expand the World Cup to 40 teams.
But his idea now is that 32 teams take part in a preliminary knockout round in the host country, with the winners joining 16 seeded teams in the group stages.
“It means we continue with a normal World Cup for 32 teams, but 48 teams go to the party,” said Infantino, who replaced Sepp Blatter.
“Fifa’s idea is to develop football in the whole world. The World Cup is the biggest event there is. It’s more than a competition, it’s a social event.”
Richard Conway, BBC Radio 5 live sports news correspondent
This is all part of Gianni Infantino’s plan to expand the tournament because there is a lot of discontent from some continents who feel World Cup places are not allocated in the right way.
It could be something like England against Iceland in the first round if England were not seeded.
It is very high risk – and it would be dramatic and exciting for TV, I am sure. That is what is on the table and a decision will be made in January next year.
Confidente. Lifting the Lid. Copyright © 2015