In an interview with The Associated Press, Francesco Ricci Bitti said Rio's troubled preparations are reaching a stage where some sports may need to consider "Plan B" options for their venues.
"It's getting very serious," the Italian said. "We have an organizing committee with good people but without the leverage to cope with the problem. ... We are scared. This is not a country like China where you can ask people to work by night. In Brazil, this could not happen. The government has to change speed."
Ricci Bitti heads the Association of Summer Olympic International Federations, which represents the 28 sports in the Rio Games. He also leads the International Tennis Federation and serves on the IOC co-ordination commission for Rio, which made its latest visit to Brazil two weeks ago.
"We can be flexible in the infrastructure but surely not in the sports venues, and we are at risk at sports venues," Ricci Bitti said. "Even for the ones that don't consider themselves at risk, we don't see a sense of urgency."
The timetables are so tight that backup plans may need to be considered by some sports, he said.
"We have to sit down and to start looking at some Plan B's," Ricci Bitti said.
Rio's problems dominated discussions at the ASOIF general assembly, which took place during the SportAccord convention in this Mediterranean resort in southern Turkey. Rio will also top the agenda for meetings of the International Olympic Committee executive board, which meets here Wednesday and Thursday.
"We need to act now because if we wait another six months, as it could be looking at the inactivity of the government, I think it will become very serious," Ricci Bitti said. "The organizing committee is doing its best, but the government is not supporting enough."
Brazil is also struggling with delays ahead of hosting the World Cup this summer. With the country focusing on the World Cup, Ricci Bitti said, the Olympic preparations risk falling further behind.
"We can't always hope in the fact that in the end we will solve the problem," he said. "This time we have the style and the habits of the South Americans. They are not used to managing big events like this. The Olympics is a very different problem from the World Cup. The World Cup in the end is one stadium, one hotel, in many cities. Rio has a lot of problems."
Rio organizing committee chief Carlos Nuzman and CEO Sidney Levy were meeting in Brasilia on Tuesday with Brazilian President Dilma Rousseff's chief of staff to discuss the Olympics.
It was left to Rio's executive sports director, Agberto Guimaraes, to report to the federations in Turkey.
"I still think we can pull this thing together and can have great games," he told the delegates. "The moment I don't I will (give) my resignation. I still believe we can do it. Please help me get through this alive and well."
Christophe Dubi, the IOC's deputy executive director for the Olympic Games, said the IOC would be sending special task forces to Rio to monitor the situation. The first group will consist of construction experts, he said.
"We have to have special measures in place," he said.
Dubi noted that Gilbert Felli, the IOC's long-time executive director, has been assigned to work with Rio after he steps down from his post later this year.
The meetings in Turkey come amid a daily drumbeat of troubles in Brazil. On Monday, striking construction workers and security personnel clashed at Rio's Olympic Park. Random gunshots were fired but no injuries were reported.
Workers also went on strike Monday at the Olympic stadium that will be used for track and field at the games. The venue has been closed since last year to fix problems with the roof.
Guimaraes said the repair work would completed by December.
The greatest concerns centre on the Deodoro complex, an area that is to host venues for eight sports. Work has yet to begin on the site.
In addition, work on the Olympic golf course is far behind schedule, raising concerns for the sport's return to the games after more than a century. Guimaraes said grass would begin to be laid on the course later this month and the venue would be ready by September 2015.
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