Infantino, who had until now proposed a 48-team event but with a traditional 32 countries advancing to the finals, will submit his latest proposal at a FIFA Council meeting in Zurich on January 9-10.
A letter outlining the new format was due to be sent to the members of the FIFA Council today, the source said, adding that the format was "preferred by president Infantino."
Under the new format, the source said, "every qualified team would play at least two group matches. The top two in each group would then go through to the last 32."
Infantino, formerly Michel Platini's right-hand man at UEFA, said recently he was in favour of a World Cup jointly organised by several countries to share out the burden of providing facilities for the tournament.
"We don't want white elephants," he said in reference to stadiums that have been built for past World Cups and then left without a purpose after the tournament. "We want facilities that will last.