The police commissioner’s warnings of a looming recruitment crisis have sparked fears that a dearth of new police recruits could extend up the line, reducing the number of officers entering the higher ranks and shrinking police leadership.

As Commissioner Raymond Kelly repeated his concerns yesterday about the impact of low NYPD salaries, he also disputed reports that he openly disagreed with the mayor last week about the city’s negotiating tactics with the police unions.

The commissioner explained that his comment during City Council testimony that the city’s tradition of pattern bargaining is “not working very well for the police department” was not meant to disparage the traditional practice — embraced by Mayor Bloomberg — of ensuring parity among all city union contracts.

Instead, Mr. Kelly said his statement had been intended to criticize the method of pattern bargaining among the city’s five police unions. The system has “compacted” salaries in the upper ranks, he said, hurting the department’s ability to attract police officers to those positions.

Using the sergeant’s contract as an example, he cited the low turnout and passing rate for the sergeant’s exam this year. Under the current contract, a starting sergeant earns only about $1,500 more than a top-paid patrolman, not including overtime.

Mr. Kelly has said he anticipates that the department will only be able to fill about a quarter of its open slots for new recruits this summer, a problem he blames on the $25,100 starting salary, which he said yesterday matches the starting salary of 21 years ago.

Leaders of the city’s police unions also said a recruitment crisis this summer would extend past the department’s lower ranks.

In interviews this week, several said it worries them to see more sergeants, captains, and detectives retiring and moving on to other jobs while there are fewer officers who want to replace them.

“It’s not just starting salary, we’re losing people to retirement. We’re losing sergeants and lieutenants to other police departments. That was unheard of before,” the president of the Sergeants Benevolent Association, Edward Mullins, said. “People are not interested in getting promoted at this time.”

The sergeant’s union, like the patrolman’s union, is about to enter mediation with a state panel after reaching a stalemate with the city in the current round of salary negotiations.

Attrition is already a major problem for detectives, the president of the Detectives Endowment Association, Michael Palladino, said, noting that the number of detectives has dropped dramatically since the terrorist attacks of September 11, 2001, to about 5,500 from about 7,000. He predicted that the trend will worsen if the mayor and the police union do not reach an agreement to raise starting salaries.

The police commissioner has promised in the past to keep recruitment standards high, even in the face of a smaller pool of recruits, but Mr. Palladino said he worried about the quality of incoming officers willing to accept the lower pay who must now juggle added responsibilities after September 11.

“Now not only do we fight crime, we are counterterrorism specialists,” he said.

The president of the Captains Endowment Association, John Driscoll, who has gone 42 months without a contract, also warned that a recruitment crisis would “trickle” up to the higher ranks.

“We’re the ones that run the police department, and morale has never been lower,” he said. “That’s a scary thought.”