RIO DE JANEIRO - Visitors to Rio de Janeiro during next month's Olympic Games should not set unrealistic expectations despite the city's recent transformation, mayor Eduardo Paes said on Tuesday.

Around 10 billion dollars from the private and public sectors have been poured into new infrastructure projects like a port district revamp, a subway line, motorways, a light rail service and express bus lanes.

But just one month out from the opening ceremony, the city continues to grapple with security threats, pollution and lingering infrastructure concerns.

"What made the people who voted for Rio take notice were the typical problems that Rio has like traffic jams, floods, infrastructure issues," Paes told a news conference on Tuesday.

"That is why we won the right to host the Games... So don't expect Chicago, New York or London. We need to compare Rio with Rio."

Earlier on Tuesday, Paes was forced to play down fears about public safety, just 24 hours after he told CNN that the state's handling of security was "terrible" amid an uptick in violent crime.

Officials have also fended off claims that pollution in Guanabara bay could pose a health risk to Olympic sailors.

And while most of the city's Olympic infrastructure projects have been completed, there is doubt over whether a new subway line will be ready in time for the opening ceremony.

Delays, violence and pollution are not the only cause for concern among Rio's residents. Still fresh in their minds is the April collapse of an elevated bicycle track that killed two people just weeks after opening.