Preparations for the 2016 Rio Olympics are the "worst" ever seen, according to International Olympic Committee vice-president John Coates.
The Australian said the IOC has taken "unprecedented" action by placing experts in the local organising committee to ensure the Games go ahead.
"The situation is critical on the ground," he said.
The news comes as Brazil faces a race to be ready in time for the Fifa World Cup, which starts in 44 days.
Coates, who has been involved in the Olympics for nearly 40 years, has made six trips to Rio as part of the commission responsible for overseeing the preparations.
He added that one of the experts embedded in the local committee was a construction project manager.
"The IOC has adopted a more hands-on role," said Coates. "It is unprecedented for the IOC but there is no Plan B. We are going to Rio."
He said that, in his opinion, this was "a worse situation" than in 2004, when there were concerns about preparations for the Athens Games.
"It's the worst that I've experienced," he added. "We have become very concerned. They are not ready in many, many ways. We have to make it happen and that is the IOC approach. You can't walk away from this."
Preparations for the 2004 Athens Games were marred by delayed in construction and service delivery, but the venues and infrastructure was ultimately delivered in time.
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