The NYPD will shrink to its smallest size since 1993 if Mayor Michael R. Bloomberg has to put his contingency budget plan in place, Police Commissioner Raymond W. Kelly said.

Under the mayor's current budget plan, the department will shrink from 40,710 to 39,110 through attrition. But Kelly said that the force could shrink to 35,825 by December if the city puts its contingency budget plan into effect.

Mayor Bloomberg is counting on financial assistance from the state and federal governments and the city's unions to close the city's nearly $5 billion budget deficit in the upcoming fiscal year. If that help fails to materialize, the mayor has identified $500 million in contingency cuts to make up the difference.

This contingency plan would reduce the planned size of the department to 37,790 by pushing back the date of the next hiring class from this July to January 2003.

But a wave of retirements has left the department with 37,463 officers today, the lowest it has been in five years. So if no more recruits are hired until January and the retirements continue at their current pace, the size of the force will drop to 35,825 officers in December, the last month before the new class brings it back to 37,790.

The mayor has repeatedly expressed optimism that the city will get the help it needs and will not need to impose the contingency cuts. But several fiscal monitors, including City Comptroller William C. Thompson Jr., have expressed doubts that he will get all the aid he is seeking from Albany, Washington, and the unions.

Commissioner Kelly said he would continue to try to deploy his officers as effectively as possible, but he voiced concern about the effect contingency cuts would have on the agency's ability to police the city.

When Mayor Bloomberg announced the plan, he noted that crime has continued to fall this year and said he would change the plan if crime began to rise and it became clear that the department needed more resources.