NEW YORK (AP) — Mayor Bill de Blasio met privately for more than two hours Tuesday with the leaders of the New York Police Department's unions, aiming to mend a rift with rank-and-file officers that has threatened to overwhelm his young mayoralty.

While administration officials characterized the meeting as the beginning of a process to heal wounds opened by protests about police conduct and the fatal shooting of two officers, union leaders struck a more cautious note, saying that "only time will tell" if relations would improve.

"Our main concern is the safety of our police officers of every rank on the streets in the city," said Patrick Lynch, head of the Patrolmen's Benevolent Association, which represents rank-and-file officers, after the meeting.

"There were a number of discussions especially about the safety issues that our members face," Lynch continued, reading a joint statement from all five unions. "There was no resolve. And our thought here today is that actions speak louder than words and time will tell."

Lynch has been one of de Blasio's fiercest critics, saying the mayor had "blood on his hands" after the brazen daylight ambush on two officers in their patrol car earlier this month.

A person who was briefed on the meeting but not authorized to speak publicly on a private gathering told The Associated Press that Lynch repeated much of his recent public remarks accusing de Blasio of aligning himself with protesters who have created an anti-NYPD atmosphere that led to the shooting. The union leaders charged that de Blasio had helped create an unsafe environment for police, according to the person, who spoke to the AP on condition of anonymity.

De Blasio stressed that he has not been anti-police in his remarks, imploring the unions to check the transcripts of his speeches and interviews, according to the person. He also stressed that the two sides had common ground and should table their public disagreements.

No apology was issued from either side, the person said.

Relations between the unions — who are seeking a new contract — and the mayor have been poor from the time he took office a year ago. But the anger of many officers toward de Blasio in recent days has been striking.

Twice in the last week — including at a funeral for one of the slain cops — officers have turned their backs to the mayor. And de Blasio received boos and heckles from some in the crowd Monday at a NYPD graduation ceremony.

At the mayor's behest, Police Commissioner William Bratton invited the union leaders and other top NYPD officials to join him and de Blasio for the meeting at the new police academy in Queens.

De Blasio did not take questions from reporters but his press secretary said in a statement that the meeting "focused on building a productive dialogue and identifying ways to move forward together."

"The mayor and police commissioner remain committed to keeping crime in New York City at historically low levels," Phil Walzak said in the statement, "supporting the brave men and women in uniform who protect us every day, and finding ways to bring police and the community closer together."

The two sides pledged to meet again, though no timeframe was issued. There was no discussion about whether police would again turn their backs on de Blasio at the second officer's funeral this Sunday, the person briefed on the meeting said, though the head of the NYPD Captains Endowment Association has asked his members to abstain from the act.