Mayor Michael Bloomberg said Monday that the city will need to close firehouses if the FDNY doesn't make staff cuts at 60 engine companies. A deal that allows five firefighters, rather than four at those companies, expired on Monday — and the city does not plan to renew it.

Bloomberg said most of the city's nearly 200 engine companies already operate with four firefighters.

"The fire department is going to have to spend less money just like police and sanitation and corrections and everything else," he said. "We just don't have the money and Albany cutting back will exacerbate the problem."

The FDNY estimates that the cuts will save $30 million annually in overtime costs.

But the Uniformed Firefighters Association of Greater New York and the Uniformed Fire Officers Association said the staffing reduction is a threat to public safety. They also said the city has to negotiate the longstanding deal.

The UFA and the UFOA have filed legal papers against the city seeking arbitration and an injunction to halt the cuts.

"When you reduce firefighter staffing by one firefighter, it doubles the time it takes to begin getting water on a fire and allows fires to double in size every minute," said Steve Cassidy, President of the UFA, in a statement announcing the legal action.

Bloomberg said he's confident the city will win the lawsuit.

"If we were to lose the lawsuit, I don't think there's any question, we would have to close firehouses, which is the last thing we want to do," he said.