A New York City policeman slain with his partner in an ambush will be remembered this weekend with a wake and a funeral expected to draw thousands of officers, against a backdrop of frayed relations between the force and Mayor Bill de Blasio.

Saturday's wake and Sunday's funeral for Wenjian Liu, believed to be the first Chinese-American police officer killed in the line of duty in the city, follows observances for his partner, Rafael Ramos.

Liu, 32, and Ramos, 40, were shot to death on Dec. 20 as they sat in their squad car in Brooklyn. Their killer, Ismaaiyl Brinsley, who killed himself soon after, had said he was seeking to avenge the deaths this summer of two unarmed black men at the hands of white police officers.

The killing of the officers deepened a rift between the force and the liberal mayor, who criticized the New York Police Department's stop-and-frisk policy in his 2013 run for office and offered qualified support for protests over the black men's deaths.

Since the officers were killed, some uniformed police have taken to displaying disdain for de Blasio by turning their backs on the mayor during public appearances.

In addition, the number of arrests and court summonses in the city has plummeted.

Ed Mullins, president of the Sergeants Benevolent Association, one of several city police unions, was among those who turned their backs on de Blasio as the mayor arrived at the hospital where Liu and Ramos were declared dead.

Mullins said he did not know whether officers intended to repeat the gesture at Liu's funeral, as thousands of police did last weekend as the mayor began his eulogy for Ramos.

"I don't think I have the right to interfere in their First Amendment rights," Mullins said in a telephone interview on Friday.

Police Commissioner Bill Bratton has called the wordless protests inappropriate.

Ramos' funeral was among the largest in NYPD history. U.S. Vice President Joe Biden and other dignitaries joined thousands of law enforcement officers from around the country who filled the streets outside the church where the funeral was held.

Local newspapers have said the drop in police activity is evidence of a work slowdown by officers who fear for their safety and have been angered by the months of protests across the country.

City Hall and NYPD officials have been unable to answer questions on whether a slowdown is under way since the statistics were first reported on Tuesday. Unions have said they did not order a work action.

De Blasio, who ran for mayor on a promise that he would mend strained relations between police and civilians, has avoided taking questions from reporters for nearly two weeks.

He met with police union leaders for two hours on Tuesday. The Detectives Endowment Association's president, Michael Palladino, said in a statement that there had been no resolution, "most likely due to some ideological and philosophical differences."

Although they have denied a formal slowdown, Mullins and other union leaders have encouraged members to not skirt department rules that may seem time-consuming, including waiting for backup to arrive, in the interest of safety.

Mullins believed police were still responding to emergencies as before, even if they were issuing fewer tickets for minor violations. "Car stops are a very dangerous aspect of police work," he said. "The public should be happy."

Liu's funeral will be held at Aievoli Funeral Home in Brooklyn, not far from where Liu lived with his wife of two months and his parents.

In a sign of the police force's broadening ethnic diversity, Chinese and Buddhist funeral customs are expected to be melded with the usual traditions of an NYPD funeral, which date to a time when the force was almost entirely Roman Catholic men of Irish or Italian descent.

Bratton has posthumously promoted Ramos and Liu to the rank of detective first grade, and the city has announced that two streets in Brooklyn will bear their names.