Brazilian football legend Pele has cast doubts over the nation's ability to host the 2014 World Cup and then the Olympics in Rio de Janeiro in 2016.
Speaking in London, he said: "At the moment, things are not great. We have a little problem with the construction."
He said communication and transport problems were the biggest issues, but hoped they would be resolved.
"People are saying it will be easy, but I do not think it will be - we have only two years," he added.
"I spoke with President Dilma [Rousseff] and she said she is going to do her best to organise things, but we are not ready yet."
There were similar concerns over the readiness of Athens ahead of the 2004 Olympics and South Africa in the build-up to the 2010 World Cup.
The Brazilian, 71, who has become a worldwide ambassador for football, said he hoped Brazil's first Olympics could make a big impact.
"The same company who organised the Olympics here will be in Brazil. In London, the organisation has been fantastic.
"But we (Brazil) have a lot to show the world and a lot to offer."
London's Olympic Games have seen Jamaican sprinter Usain Bolt defend his 100m and 200m sprint titles.
Asked whether Bolt had joined him and boxer Muhammad Ali as one of the greatest sportsmen of all time, Pele, who was voted Athlete of the Century by the International Olympic Committee in 1999, responded: "Yes, no doubt."