NEW YORK (CBSNewYork/AP) — The rift between Mayor Bill de Blasio and police union leaders remains after the two sides met privately for more than two hours Tuesday, aiming to mend tensions with rank-and-file officers.

A message about the rift was seen in the skies over the city on New Year’s Eve.

On Wednesday afternoon, a plane over the Hudson River was seen pulling a banner reading, “De Blasio, apologize to the NYPD.” The banner was paid for by a group of retired and current NYPD officers.

The same group used a banner plane last week to send another message, that one reading, “De Blasio, our backs have turned to you.”

Administration officials characterized the meeting on Tuesday as the beginning of a process to heal wounds opened by protests about police conduct and the fatal shootings of officers Rafael Ramos and Wenjian Liu. But union leaders struck a more cautious note.

“There was no resolve,” said Patrick Lynch, head of the Patrolmen’s Benevolent Association. “Actions speak louder than words and time will tell.”

No apology was issued from either side, a person who was briefed on the meeting told The Associated Press.

Union leaders have said the mayor fostered an anti-NYPD atmosphere that contributed to the officers’ deaths.

“Our main concern is the safety of our police officers of every rank on the streets in the city,” Lynch said. “There were a number of discussions especially about the safety issues that our members face.”

Lynch has been one of de Blasio’s fiercest critics, saying the mayor had “blood on his hands” after Ramos and Liu were ambushed and killed earlier this month.

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 Ramos’ funeral, officers have turned their backs to the mayor. De Blasio also received boos and heckles from some in the crowd Monday at a NYPD graduation ceremony.

At the mayor’s behest, Police Commissioner Bill 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.

The meeting happened right after the NYPD released new crime statistics showing that arrests have dropped 66 percent since the officers’ deaths.

The NYPD denies the existence of a coordinated work slowdown as part of the continuing rift between the police force and de Blasio.

It says the drop in arrests is due to a combination of officers grieving and being on edge after the fatal shootings of Liu and Ramos and not making unnecessary stops and summonses.

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