"We will encourage co-hosting for the World Cup because we need FIFA to show we are reasonable and we have to think about sustainability long-term," Infantino said.
"(We could) ...maybe bring together two, three, four countries who can jointly present a project with three, four, five stadiums each. We will certainly encourage it. Ideally the countries will be close to each other."
His remarks could open the way to a joint bid from the United States, Canada and Mexico, which have already said they intend to hold discussions over the possibility.
At the end of last year Victor Montagliani, president of the Concacaf federation that the three countries belong to, said he expected formal discussions to start once "all the rules and regulations" related to the bid were announced.
Concern has been raised about the financial burden placed on a single tournament host, and the bad publicity generated by stadiums built and then abandoned after use.
The only time FIFA has previously sanctioned co-hosting was in 2002 when Japan and South Korea staged a tournament that was widely heralded as a success.
The idea has taken off at the European Championship, with Belgium and the Netherlands co-hosting in 2000, Austria and Switzerland in 2008 and Poland and Ukraine in 2012. The next tournament in 2020 has been designated as Pan-European and is due to be staged in 13 cities in 13 counties.
Swedish FA chair Karl-Erik Nilsson quickly backed co-hosting for the World Cup too.
"It's a good idea, and Europe has of course previously worked in this way on the European Championships," he said.
"We are used to it and it works well, it makes it possible for more countries to arrange (tournaments), and in that way it is positive."
But there is likely to be opposition from fans' groups, given the higher cost involved in following a team through different countries.
Joint hosting could also raise security concerns.
Brazil's Maracana, which staged the last World Cup final in 2014, has become unusable in recent months, sitting with rusting gates and with a badly damaged playing area following a dispute over repair costs and redevelopment.
(Reporting by Tom Finn, writing by Sami Aboudi; Editing by Toby Chopra and John Stonestreet)
