FIFA want all 32 teams that have qualified for Brazil 2014 to send in their schedules from March 1 to give football's international governing body the opportunity to test players for doping in the lead-up to the World Cup finals.
Dvorak, FIFA's chief medical officer, explained players and teams will not know when the drug testers will arrive but promised no-one will be missed before Brazil play Croatia in the first match of the tournament on June 12.
"I am happy that you are insecure about when we will start the doping controls because we won't make it public," Dvorak said.
"We can come anytime, anywhere, if we decide to.
"So we will definitely disclose the strategy as to when we are going to test the French team, we will come. So leave it with us.
"We are asking, as from March 1, for the whereabouts of each teams. And then we will decide at the headquarters when we'll go where.
"To make it very clear, we will test all players participating in the World Cup at least once prior to the kick-off game."
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