Speaking during a visit to the northeastern city of Fortaleza, FIFA's secretary-general Jerome Valcke said cities were legally bound to stage the open-air fan events, which will provide live broadcasts of matches on giant screens, reported Xinhua.
"The cities who have not yet committed to have their own fanfest, it's a mistake, and they have to do it, there is no choice," Valcke said.
"There must be a fanfest in each of the 12 host cities in Brazil. That's a must."
Among cities to express doubt whether to stage fanfests are Recife and Rio de Janeiro.
The prefecture of Recife says it does not have the money to pay for the event, while government officials in Rio are concerned at the prospect of violent protests at public venues.
FIFA has agreed to pay for giant screens and security fencing with local prefectures and the private sector asked to cover other costs.
In March FIFA warned that cities were contractually bound to stage the fanfests and that they face legal action if they refused.