The athletes' union in Brazil is warning government officials, the local football federation and FIFA that early afternoon matches in tropical cities may jeopardize players' health during the 2014 World Cup.

The union said Tuesday it notified Brazil's Sports Minister Aldo Rebelo and the Brazilian football federation that it is against the kickoff times announced by FIFA last week.

Union president Rinaldo Martorelli told The Associated Press that the body will take all available measures to keep the matches from being held at the hours established by FIFA, including legal actions.

FIFA detailed group-stage kickoff times with the northeast cities of Natal, Recife and Salvador each hosting two matches at 1 p.m. local time (1600 GMT). The tropical city of Fortaleza will host a 1 p.m. second-round match.