In an unusually blunt public warning Tuesday, a vice president of the International Olympic Committee (IOC) called the preparations for the 2016 Games in Rio de Janeiro "the worst I have experienced."

John Coates, who has made six trips to Brazil as part of the IOC's coordination commission for Rio, said the Brazilians, who beat out Spain to win their Olympic bid less than five years ago, are behind schedule and that there is no backup plan to move the games anywhere else.

"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," Coates said.

The 2016 Games, which will be the first played on the South American continent, have been plagued by delays, rising costs and bad communication between different levels of the Brazilian government and organizers, prompting criticism from international sports federations.

Brazil has also come under fire from football's world governing body, FIFA, for long delays in the construction of stadiums and other infrastructure and the overdue completion of venues for the World Cup, which kicks off in June. But two years out from the 2016 Olympics, that situation appears even bleaker.

Attending an Olympic forum in Sydney, Coates told delegates that construction had not commenced on some venues, infrastructure was significantly delayed and water quality was also a major concern. And until recently, over 2,000 construction workers, who were seeking higher wages and more benefits, had been striking at the main Olympic park outside of central Rio.

"I think this is a worse situation than Athens," said the Australian, referring to preparations for the 2004 Games, which were also plagued by construction delays.

"In Athens, we were dealing with one government and some city responsibilities. Here, there's three," Coates said. "There is little co-ordination between the federal, the state government and the city — which is responsible for a lot of the construction."