FIFA said Friday that their decision to play 2014 World Cup matches in the early afternoon in Brasilia, where the dry winter air can be at its most crushing, was not motivated by commercial interests.
Five matches will kick-off at 1300 local time in the Brazilian capital, a decision that has proved controversial.
"The health of the players and the quality of the matches are the priorities above all other considerations," said FIFA secretary-general Jerome Valcke, who was irritated by a question posed by a Brazilian reporter who had argued that the tournament was being dictated by European television demands.
"When you have 64 matches on the programme that must be played in the space of 30 days, you cannot avoid certain teams playing at 1300," added FIFA president Sepp Blatter.
"History shows that the good players play in all temperatures. Take Mexico in 1986, we played at mid-day at 2,000-2,800m (6,500 to 9,000 feet) altitude and the quality of the games did not suffer."
Valcke added that the local organising committee as well as medical authorities had supported the early starts.
"We have chosen to have matches in all of Brazil because that was the wish of Brazil," he said.
"The decision was taken so that all Brazilians get the chance to see England, Germany, Italy, the top teams who could qualify."