New York City Mayor Bill de Blasio called Monday for a pause in protests over police conduct as he faced a widening rift with those in a grieving force who accuse him of creating a climate of mistrust that contributed to the execution of two officers.

“I think it’s important that, regardless of people’s viewpoints, that everyone step back,” de Blasio said in a speech Monday at the Police Athletic League. “I think it’s a time for everyone to put aside political debates, put aside protests, put aside all of the things that we will talk about in all due time.”

De Blasio’s relations with the city’s police unions have tumbled to an extraordinary new low ? one not experienced by a mayor in the nation’s largest city in more than a generation ? in the aftermath of Saturday’s shooting in which the gunman claimed was retaliation for the deaths of black men at the hands of white police. In a display of defiance, dozens of police officers turned their backs to de Blasio at the hospital where the officers died, and union leaders said the mayor had “blood on his hands” for enabling the protesters who have swept the streets of New York this month since a grand jury declined to indict an officer in the chokehold death of Eric Garner.

De Blasio, in his first extensive remarks since the killings, called for “everyone to put aside political debates, put aside protests, put aside all of the things that we will talk about in all due time.”

“We are working toward a day where we can achieve greater harmony toward policing and community,” he said later Monday.

Officers Wenjian Liu and Rafael Ramos were ambushed Saturday afternoon by a 28-year-old who vowed in an Instagram post that he would put “wings on pigs.” The suspect, Ishmaaiyl Brinsley was black; the slain New York Police Department officers were Hispanic and Asian.

The killings came as police nationwide are being criticized following Garner’s death and 18-year-old Michael Brown’s fatal shooting in Ferguson, Missouri. Protests erupted after grand juries declined to charge officers in either case.

On Monday, a prosecutor said a white Milwaukee police officer who was fired after he fatally shot a mentally ill black man in April won’t face criminal charges. Lawyers for the slain man’s family urged any protesters there to be peaceful.

De Blasio said it was time to focus on the officers’ grieving families. He and Police Commissioner William Bratton met with them earlier Monday.

“There’s a lot of pain. It’s so hard to make sense of it ? how one deeply troubled, violent individual could do this to these good families,” a somber de Blasio said. “And I think it’s a time for everyone to take stock that there are things that unite us, there are things that we hold dear as New Yorkers, as Americans.”

Investigators said Brinsley was a bystander during a protest two days before the Garner grand jury decision but had not participated. It remained unclear if Brinsley simply latched onto the cause for the final act in a violent rampage that began Saturday morning in Baltimore when he shot his ex-girlfriend in the stomach. The woman said Brinsley had first held the gun to his own head but she talked him down, authorities said.

Police are trying to determine Brinsley’s whereabouts in the two hours he was in New York before killing the officers. Video gathered by police shows Brinsley holding a foam food container that investigators believe held the gun he used. After the shooting, he then ran into a nearby subway station and killed himself.

The police unions blame de Blasio for fostering an anti-police sentiment. Patrolmen’s Benevolent Association President Patrick Lynch declaring that there was “blood on the hands” on the “steps of City Hall and the office of the mayor.”

Sergeants Benevolent Associations head Edward Mullins refused to back down from that stance, saying in an interview Monday that “the mayor has turned his back on us ? he got elected on his campaign of attacking the police all along.”

That link ? strenuously denied by the de Blasio administration ? was given some credence by Police Commissioner William Bratton on Monday. In an interview with NBC, Bratton said “what’s quite apparent, obvious, is that the target of these two police officers was a direct spinoff of this issue of these demonstrations.”

Even Bratton, who has steadfastly praised de Blasio, conceded that the mayor was on shaky footing with some in the NYPD. When asked on NBC’s “Today” show if the mayor had lost the force’s trust and confidence, Bratton said, “I think he’s lost it with some officers.”

Later Monday, Police Commissioner William Bratton said he had met with representatives from the five unions who agreed to stand down.

“And then we can continue the dialogue that had begun about issues and differences that exist,” Bratton said.

Meanwhile, big-city police departments and union leaders around the country were warning the rank and file to wear bulletproof vests and avoid making inflammatory posts on social media.

A union-generated message at the 35,000-officer NYPD warned officers that they should respond to every radio call with two cars ? “no matter what the opinion of the patrol supervisor” ? and not make arrests “unless absolutely necessary.” The president of the detectives’ union told members in a letter to work in threes when out on the street, wear bulletproof vests and keep aware of their surroundings. At the same time, a memo from an NYPD chief asked officers to limit their comments “via all venues, including social media, to expressions of sorrow and condolence.”

One directive warned officers in Newark, New Jersey, not to patrol alone and to avoid confrontation. In Philadelphia, Police Commissioner Charles Ramsey urged protest leaders to “call for calm and not let this escalate any further.” Boston’s police commissioner said officers there were on alert.

Officials in New York investigated at least a dozen threats against police since the shootings, and one man was arrested at a Manhattan precinct after he walked in and said: “If I punch you in the face, how much time will I get?” and refused to leave.

(AP)