The Council voted 49-0 to authorise Mayor Richard Daley to sign the International Olympic Committee's (IOC)  Host City contract that means taxpayers will be responsible for the Olympics and a proposed $4.8 billion (£2.9 billion) operating budget.

Chicago was the only one of the four candidates bidding to follow London 2012 and host the 2016 Olympics that did not have financial guarantees, a situation that some experts believe has led to the United States city slipping from its position as favourite to now being behind Rio de Janeiro going into the final vote at the IOC Session in Copenhagen on October 2.

Patrick Ryan, the chief executive and President of Chicago 2016, hailed the deal.
 

He said: "We are joining the ranks of the other three so that no longer will we be at a competitive disadvantage by virtue of this so-called guarantee."

Madrid and Tokyo, who are the other cities short-listed to host the Olympics, like Rio, have guarantees from their Governments.
 

Daley needed the Council's approval after promising to sign the IOC contract in June to allay any concerns about the city's commitment.

An IOC Evaluation Commission Report published last week had highlighted Chicago's lack of a full financial guarantee.

Daley said: “I’m grateful to the Aldermen and our residents for the critical role they’ve played in making Chicago’s bid to host the Games the strongest ever put forward by our country.

“Chicago 2016 will head to Copenhagen in less than 30 days, and with today’s decision, we are sending a message to the world that Chicago wants the Olympic Games to be held here.

"This is not about Richard J. Daley or Richard M. Daley's legacy.

"This is about the city of Chicago.

"The Olympics and paralympics is bigger than me."
 

Several Aldermen said they could approve the contract while minimising the risk to taxpayers because local bid officials have lined up more than $1.4 billion (£846 million) in insurance to protect the operating budget.
 

Aldermen Toni Preckwinkle said: "[It] really gives those of us in Government confidence that there's a real layer of protection between us and the necessity for putting in any either city or state resources."

Ryan said: “This is a huge day for our bid.

“Today’s successful outcome is the result of an incredibly collaborative effort by the Mayor, the City Council and our bid, and it epitomises everything the world has come to expect from Chicago -transparency, competence and an ability to deliver.

"I’m thankful to the Aldermen for their support and excited about the momentum the vote gives our team heading into the final weeks of this campaign.

"Our vision for hosting the Games is to deliver a spectacular sport experience for the athletes of the world and, as the IOC Evaluation Commission noted in their Report last week, turn ‘the centre of the city into an Olympic playground'.

"But we’ve also been ever-mindful of our responsibility to develop a plan that was financially responsible and will leave a sustainable urban, sport, social and environmental legacy for the community.

"The Chicago City Council has agreed our plans do just that.

"As we head to Copenhagen next month, we’re hopeful that the voting members of the IOC agree.”
 

But a group that opposes Chicago's bid said Aldermen had abdicated their responsibility to taxpayers.

Tom Tresser, a spokesman for No Games Chicago, said: "The City Council endorsed the mayor's blank check to the 2016 Olympic bid."

Ryan said: "How could you be against something that is so good for the city?

"Unless you do it wrong."