Kerry, meeting with Brazilian Foreign Minister José Serra in Rio before the opening of the Games later on Friday, told reporters he was sure Brazil will deliver "not just a great venue but a great Olympics."
The Rio Olympics, the first to be held in South America, are being held at a time of heightened concerns of terrorism following attacks in European cities inspired by Islamist extremism.
Brazil has deployed troops to patrol Rio's emblematic tourist sites to guard against the slightest chance of an attack, officials said, though security at the Olympic stadium appeared slack on Tuesday.
Security concerns jumped last month after Brazilian police, acting on a tip from the U.S. Federal Bureau of Investigation, detained 12 people on suspicion of links to the Islamic State militant group.
Some two dozen heads of state and government and 50,000 spectators are expected to attend the torch ceremony at Rio's Maracana stadium on Friday night, with some 3 billion people tuning in around the world.
(Reporting by Paulo Prada and Anthony Boadle; Editing by Jonathan Oatis and Leslie Adler)
