New York City Mayor Bill de Blasio was expected to return from Germany Sunday night amid criticism over his decision to attend a G-20 summit protest there following the fatal shooting of an NYPD officer in the Bronx.

The head of the NYPD’s sergeants union, in a Sunday morning radio interview, denounced de Blasio’s Hamburg trip late Thursday to be the keynote speaker at the rally.

“New York City right now is mourning the loss of a police officer who was dedicated to the city of New York, and we have our mayor who’s just gone to Germany to join protesters,” Sergeants Benevolent Association president Ed Mullins said during an appearance on “The Cats Roundtable” on 970 AM.

The mayor announced the trip abruptly, a day after Officer Miosotis Familia was shot to death in the Bronx by an ex-convict with a history of mental illness as well as railing against cops on social media. The gunman, Alexander Bonds, 34, of the Bronx, was later and shot and killed by NYPD officers.

Mullins accused de Blasio of contributing to an “anti-police atmosphere,” saying that six NYPD officers have been killed during the mayor’s first term in office, compared with one fatality in the final four years of his predecessor Michael Bloomberg.

“We’re not seeing any type of leadership that comes out and explains . . . the police are not your enemy,” Mullins told the show’s host John Catsimatidis, a former Republican mayoral candidate.

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Mark Penn, a prominent Democratic campaign strategist and former adviser to Bill and Hillary Clinton, also appeared on Catsimatidis’ show and called the timing of de Blasio’s trip “unbelievable.”

“I was stunned, given that the police officer was assassinated,” Penn said.

De Blasio defended the trip, saying it was in the works about two weeks before the fatal shooting and came at the invitation of local German officials.

“All the issues that need to be attended to, I’m attending to every day, regardless of where I am,” de Blasio said Friday in a radio interview from Hamburg on WNYC, later adding, “I feel so deeply for Officer Familia’s family.”

The wake and funeral for Familia, 48, will take place Monday and Tuesday at the World Changers Church in the Bronx, according to the NYPD. The wake, which is expected to be open to the public, is Monday from 2 to 4 p.m. and 7 to 9 p.m. The funeral service will take place at 10 a.m. on Tuesday. Officials have said 25,000 mourners are expected at the funeral.