"I don't think its a good idea to dilute the sporting value (of the tournament)," the 2014-World Cup winning coach told the Welt am Sonntag newspaper in an interview on Sunday.
Loew added that he had "an absolute understanding for the smaller nations who, thanks to this, could take their place on the big stage."
However, Loew, who was also against enlarging the European championship from 16 to 24 teams, said that expanded tournaments placed a greater "sporting and mental" burden on the players.
"We must be clear that, in the long term, the quality suffers," he said. "We must not overdo it."
Infantino made enlarging the World Cup from 32 to 40 teams a key point in his successful campaign for the FIFA presidency.
The FIFA Council is due to discuss the proposal, which would be implemented for the 2026 World Cup, at its next meeting on Oct. 13-14.
(Writing by Brian Homewood, editing by Pritha Sarkar)
