World football's governing body is not interested in altering the start of some matches in Brazil and said decisions on water breaks will be made on a game-by-game basis
This week, the union filed a lawsuit to try and force Fifa to change the times of the 24 matches that are scheduled to start at 13:00 local time (17:00 CET), arguing that the intense heat and humidity in some venues will put players at risk.
Fenapaf has insisted that, at the very least, two minute water breaks must be taken at the midway point of each half during such games.
However, Fifa have ruled out changing kick-off times for next month's tournament.
"Fifa's medical team is always monitoring carefully all venues during any Fifa competition to protect the players' health," the organisation indicated in a press release.
"Cooling breaks will be considered on a match-by-match basis for the 64 matches. Official and mandatory cooling breaks will not be pre-established. Rather, climate conditions will be evaluated prior to each match by the Fifa venue medical officer.
"One core aspect in defining the kick-off times was the very thorough analysis of the historical climate data in all venues.
"Therefore, the venues with the highest average temperatures such as Manaus, Cuiaba and Fortaleza do not have any matches with 13:00 kick-off times during group stage."
Fenapaf insists the changes are required based on local labour regulations and a study conducted by Brazilian sports doctor Turibio Leite.
Union president Rinaldo Martorelli told Associated Press: "We've been trying to discuss this with Fifa for nearly two years and they won't even sit down to talk to us.
"The only alternative was to seek legal action. We really hope that they make the changes in kick-off times, but if that doesn't happen, they need to at least make the cooling breaks mandatory."