Elected officials are forecasting that decade-long reductions in the city’s crime rate will come to an end if the police department follows through with a proposal to cut the size of its force.

The predictions came yesterday at a budgetary hearing at City Hall, where Police Commissioner Raymond Kelly fielded questions and listened to City Council members’ concerns about proposed cost-saving measures, called for by Mayor Bloomberg, that could reduce the number of officers patrolling the city’s streets.

“Your force is so overextended that it will not be able to continue to make the gains we we’ve seen in the past,” the chairman of the council’s Committee on Public Safety, Peter Vallone, told Mr. Kelly.

The commissioner’s plan to cut the department’s head count by 1,000 officers, a move that would save about $50 million in fiscal years 2008 and 2009, until recently attracted little criticism. The department is already about 2,000 officers short of its hiring goals, which Mr. Kelly attributes to the low starting salary, so it was thought the department would only be cutting fat.

However, Mr. Vallone and several other officials pointed out that an arbitration board is expected to reach a decision by the summer over a new starting salary for officers that will likely be much higher than the present $25,100. The department would then have little trouble filling vacant positions, they said.

Compounding the council’s concerns, Mr. Kelly said that, because of worsening economic conditions, Mr. Bloomberg has asked city agencies to reduce their budgets by another 3%.

“In order to meet this target, further reductions to the uniformed head count would be required and could include delays and/or the elimination of future police officer hiring classes,” Mr. Kelly said. The president of the Patrolmen’s Benevolent Association, Patrick Lynch, called on the council to reject the proposed cuts, saying in a statement that staffing would be at its lowest since 1992, when the city had a much higher crime rate.

While Mr. Kelly said he disagreed with several council members who said there are already signs that crime is rising, he said it is in the city’s interests to maintain a robust police force.

The council also heard concerns from the city’s district attorney’s offices, and Mr. Vallone faulted the city for forcing prosecutors to cut their budgets significantly.

The Manhattan district attorney, Robert Morgenthau, whose office will have to reduce its budget by $5.7 million, said the cuts would hamper his office’s ability to prosecute criminals.