New York City Mayor Bill de Blasio said on Thursday a proposal to rein in horse-drawn carriages had collapsed after the labor union that helped negotiate the compromise withdrew its support.

The abrupt reversal came just one day before the City Council was set to vote on a bill that would have cut the number of drivers from 220 to 95. The loss of union backing for the deal was a political setback for de Blasio, who pledged during his 2013 campaign to eliminate the iconic carriages.

The Teamsters local union, which represents carriage drivers and had worked with de Blasio to craft a deal that stopped short of a total ban, said on Thursday it had decided it could no longer support the legislation.

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"With the legislation now finalized, our members are not confident that it provides a viable future for their industry," union President George Miranda said.

Earlier this week, the union had acknowledged the bill was not ideal but said "the goal has always been to preserve this industry."

In a statement, de Blasio said the Teamsters had backed away even though nothing had changed.

"While we are disappointed this bill will no longer be considered Friday, the people of this city know what I believe, and we will work toward a new path on this issue," he said.

Under the bill, horse-drawn  carriage s, which currently offer limited rides on city streets, would have been prohibited from doing so. The city would also have converted a portion of the park into a stable that would house all  carriage  horses by October 2018.