Infantino believes "a fundamental point" for an expanded finals would be to have it co-hosted "by several countries".
He also declared himself "quite happy and confident for the future" of the scandal-tainted world governing body of football.
"Nobody is perfect, I am the last to be. But I don't steal, I don't profit, I don't cheat and I don't want to allow anyone in this organisation to do so," he said.
He had already suggested that he would be in favour of a 40-team World Cup, up from the current 32.
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"The idea would be that the best 16 teams in qualifying would qualify directly for the group phase."
He confirmed that the 32 other teams would dispute a play-off round from which the winners would enter the next stage to join the other 16 countries.
"From the point of view of the promotion of football, there would be '16 finals' before the real start of the group phase, real matches taking place to determine the 16 teams."
Swiss-Italian lawyer Infantino said that the projected increase to 48 teams "is certainly going to be discussed on October 13 and 14 when the next FIFA Council meets".
"It's a project, it's an idea just as the World Cup with 40 teams is already on the table with groups of four or five teams.
The suggestion to widen the World Cup to 48 countries is bound to generate mixed emotions.
The 2016 European Championship in France, organised by Infantino's former employers at UEFA, featured 24 teams in a month-long tournament with just eight countries being eliminated at the end of the first stage.
Infantino believes a 48-team World Cup would represent "a
high sporting level because from each play-off the best teams would qualify.
"People talk a lot about a decline in the standard but in my opinion the quality of the Euros was not less good, on the contrary. There were teams who you could not imagine could be so strong and the level was very high."
Infantino, who was the right-hand man of suspended Michel Platini in his UEFA career, believes he has the desire and the personnel to put FIFA's dark days behind them.
He underlined the importance of the work "of the new general secretary Fatma Samoura, the development of women's football and the integration of former players like Zvonimir Boban, assistant secretary general, and Marco Van Basten in the area of technical development".
"There is obviously still work to do but I am quite happy and confident about the future.