A day after the funeral of one of two police officers gunned down in their patrol car, New York City's police commissioner called Sunday for a "lot less rhetoric and a lot more dialogue" to defuse the tension between police officers and the minority communities they protect.

Speaking on NBC television's "Meet The Press," Commissioner William Bratton said the "pent-up frustrations" that have caused people to take to the streets in recent weeks go far beyond policing policies across the U.S.

"This is about the continuing poverty rates, the continuing growing disparity between the wealthy and the poor. It's still about unemployment issues. There are so many national issues that have to be addressed that it isn't just policing, as I think we all well know," he said.

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Bratton said rank-and-file officers and much of America's police leadership feels under attack, including "from the federal government at the highest levels."

He urged: "See us. See the police. See why they have the anxieties and the perceptions they have."

Bratton also appeared on CBS' "Face the Nation," where he defended Mayor Bill de Blasio, saying it was wrong for hundreds of police officers to turn their backs to a video monitor outside a Queens church as de Blasio spoke at the funeral of slain Officer Rafael Ramos.

"I certainly don't support that action," he said. "That funeral was held to honour Officer Ramos. And to bring politics, to bring issues into that event, I think, was very inappropriate."

He acknowledged, though, that the morale of officers is low and said their actions "unfortunately" reflected the feelings of some toward the mayor. Some police officers blame de Blasio for creating an atmosphere of negativity toward the New York Police Department in the city after a grand jury declined to charge an officer in the police chokehold death of Eric Garner on Staten Island.

The gesture at Ramos' funeral came amid contentious contract negotiations with the city. The rank-and-file police union did not claim credit for the symbolic protest, and its head, Patrick Lynch, repeatedly dodged reporters' attempts to ask about it after Ramos' funeral.

It was not clear if officers planned to turn their backs on de Blasio again at the funeral for Ramos' partner. Arrangements for that service have not yet been announced.

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The silent protest was a continuation of the defiance shown at a hospital after the officers' slayings on Dec. 20, when Lynch and others turned their backs on de Blasio. Lynch said the mayor had "blood on his hands."

Bratton said de Blasio was "totally supportive" of officers and had contributed hundreds of millions of dollars outside the department's budget this year, much of it focused on officer safety enhancements.

After Bratton, former Mayor Rudolph Giuliani told the CBS program that it was wrong for officers to turn their backs on de Blasio or to try to blame him for officers' deaths.

But he also said de Blasio should apologize to the police department because he "created an impression with the police that he was on the side of the protesters."

"Say you're sorry," Giuliani urged.

De Blasio stayed out of sight Sunday, staging no public events and continuing to let Bratton hold centre stage in the week since the double murder.

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Ramos and his partner, Wenjian Liu, were shot to death as they sat in their patrol car in daylight. After the officers' deaths, the gunman, Ismaaiyl Brinsley killed himself. Police said he was troubled and had shot and wounded an ex-girlfriend in Baltimore earlier that day.

In online posts shortly before the attack, Brinsley referenced the killings of two unarmed black men by white police officers — Michael Brown in Ferguson, Missouri, and Garner, in the New York borough of Staten Island.

Bratton said the department had recently investigated more than 50 reports of threats against officers, closing out over half of them with nine arrests, and had warned officers to be alert to potential dangers. More than 20,000 officers attended Ramos' funeral, along with Vice-President Joe Biden