Brazil's top Olympic official Carlos Nuzman said on Saturday there was no way to completely guarantee public safety during next month's Olympic Games.
But Nuzman vowed organizers would provide the best possible security to athletes, officials, local residents and an estimated 500,000 visitors.
"We are going to have the largest Olympic security contingent ever, but we are also going to be hoping because nobody can control what is happening in the world today," Rio 2016 chief Nuzman told reporters.
Nuzman's comments came less than two days after 84 people were killed, including at least 10 children, when a truck ploughed through a crowd celebrating Bastille Day in the southern French city of Nice.
On Friday Brazil's interim president Michel Temer convened an emergency meeting of his top security staff to discuss stepping up counter-terror efforts during the August 5-21 Olympics.
South America's largest country plans to deploy 85,000 soldiers and police during the Games, about double the number used in London four years ago.
The government has also launched an awareness campaign designed to foil possible terror plots.
The initiative involves the distribution of brochures, posters and booklets explaining how to identify people engaging in suspicious activity.
In June the government said Brazil's intelligence agencies were working alongside counterparts in the United States, England, France, Israel and Russia to avert the threat of terrorism.
