Police officers turned their backs on New York City Mayor Bill de Blasio on Sunday during the funeral for Wenjian Liu, one of two NYPD officers killed in a Dec. 20 ambush, exposing the ongoing rift between the department and City Hall.

The officers were seen turning away from an outdoor screen showing de Blasio’s eulogy at the service in Brooklyn, defying a request by New York Police Commissioner William Bratton not to protest at the funeral.

“A hero’s funeral is about grieving, not grievance,” Bratton wrote in a memo to officers on Friday, less than a week after officers turned their backs on de Blasio at the funeral of Rafael Ramos, the other NYPD slain officer. “I remind you that when you don the uniform of this department, you are bound by the tradition, honor, and decency that go with it.”

While he made “no threats of discipline,” Bratton said he did not support the actions of those officers who “stole the valor, honor, and attention that rightfully belonged to the memory of detective Rafael Ramos’ life and sacrifice.”

According to the Associated Press, thousands of officers joined in Sunday’s protest.

Bratton said he believes the divide — triggered by de Blasio’s response to the killing of Eric Garner, an unarmed black man, by a white police officer, on Staten Island — will continue for the foreseeable future.

“I think it’s probably a rift that is going to go on for a while longer,” Bratton said on NBC’s “Meet the Press” last week. “They really do feel under attack.”

“As we start a new year, a year we’re entering with hearts that are doubly heavy,” de Blasio said in his remarks Sunday, “let us rededicate ourselves to those great New York traditions of mutual understanding and living in harmony. Let us move forward by strengthening the bonds that unite us, and let us work together to attain peace.”