The mayor of Boston left the city's bid to host the 2024 Olympics hanging by a thread Monday, saying he would not sign a host agreement without strong guarantees to protect taxpayers.

A final decision on whether the bid would go ahead is up to the United States Olympic Committee (USOC), Marty Walsh told a news conference amid growing doubts about the troubled Boston bid.

"This is a commitment that I cannot make without assurances that Boston and its residents will be protected," Walsh said.

"I refuse to put Boston on the hook for overruns, and I refuse to commit to signing a guarantee that uses taxpayers' dollars to pay for the Olympics," he added.

The US Olympic Committee faces a September 15 deadline to submit a formal bid to the International Olympic Committee.

Massachusetts Governor Charlie Baker is scheduled to speak to USOC officials on Monday.

The bid group, a private entity, estimated the insurance would cost about $128 million, and would pay out in case of events being cancelled, sponsors failing to meet their obligations, or costs for lower than expected ticket sales and attendance.

But one local opposition group argued that the insurance wouldn't protect taxpayers if the budget underestimates building costs or if the scope of Olympic projects changes over time.

"I continue to believe in the potential of the Olympics and the ability to bring long-term benefits to Boston," said Walsh. But he made it clear he was prepared to let the bid go.

"I cannot commit to putting the taxpayers at risk," he said.

"If committing to signing a guarantee today is what's required to move forward then Boston is no longer pursuing the 2024 Olympic and Paralympic Games," he added.

There was no immediate response from the USOC.
Source: AFP