Dornelles, speaking in an interview with Olympics-rightsholders Globo, insisted that a "great Olympics" remains possible, but only if specific steps are taken.
"I am optimistic about the Games, but we have to show the reality," he wrote.
"We can make a great Olympics, but if some steps are not taken, it can be a big failure.
"I have said that without security and no subway, there will be difficulties.
"How will people get to places without underground transport?
"How will people feel protected in the city without security?
