NEW YORK (AP) — New York City Mayor Bill de Blasio beat back repeated calls Wednesday for him to fire the police officer accused of using a fatal chokehold on Eric Garner five years ago, saying he was obligated to keep his opinions to himself until police department disciplinary proceedings are complete.

The Democrat, who is running for president partly on his record of police reform, said he felt "it was an injustice of the highest order," that the U.S. Justice Department investigated Garner's death for nearly five years before announcing Tuesday that no civil rights charges would be filed.

But de Blasio would not say whether he believes whether the officer involved in the death, Daniel Pantaleo, should lose his job.

"I'm not going to venture personal opinions," de Blasio said. "When you're the steward of the entire city this is not about personal opinions."

Protesters marked the anniversary of Garner's death, five years ago Wednesday, with a demonstration in downtown Manhattan that drew several hundred people.

Carrying signs saying, "I can't breathe," a reference to Garner's dying words, they chanted and marched past federal courthouses toward the Brooklyn Bridge.

Garner's family members called for Pantaleo to be fired, as did several of the elected officials seeking to succeed de Blasio as mayor.

"We've been failed by every other source," Garner's mother, Gwen Carr, said Wednesday on CBS. "He should be fired. At least that would give me closure."

City Council Speaker Corey Johnson said Tuesday that Pantaleo "should have been fired months ago, if not years ago." Public Advocate Jumaane Williams said: "You cannot be president, you cannot be the Democratic nominee, if Daniel Pantaleo is still on the force."

But De Blasio said repeatedly that Pantaleo is entitled to due process. "There is a law that determines first everyone gets due process," he said in an interview on radio station Hot 97. "You would want it. I would want it. Everyone gets it."

Radio host Ebro Darden countered: "You know, look, we get along, but I do have an expectation that you're going to fire this officer. I'll be honest with you. I'll be seriously disappointed if that doesn't happen."

But de Blasio insisted, "We are following the law."

Asked at the news conference if he should be expected to at least have an opinion on a matter that has "roiled the nation," de Blasio said that being a leader "takes a lot of restraint, and being a leader takes a lot of patience, and I've learned that certainly on this job many times."

Pantaleo, who is white, placed Garner, who is black, in what prosecutors said was effectively a chokehold after Garner refused to be handcuffed during an arrest over the selling of loose, untaxed cigarettes.

Chokeholds are banned under police policy. Pantaleo maintained he used a legal takedown maneuver called the "seat belt."

The decision to end the investigation was made by Attorney General William Barr and was announced just as the statute of limitations for bringing charges was set to expire. Federal prosecutors said they didn't have evidence that Pantaleo had "willfully" violated Garner's civil rights.

De Blasio blamed the long delay in starting NYPD disciplinary proceedings against Pantaleo on the Justice Department, saying it had asked the city to delay while the federal investigation was ongoing.

"I regret that I trusted the United States Department of Justice, I really do," de Blasio told reporters at a news conference. "I grew up watching the Department of Justice act as the protector of civil rights and civil liberties and taking on racist policies, taking on state governments and local governments that were treating people unfairly and I always believed no matter how strange the politics were in our country that the Justice Department would keep to that standard."

De Blasio said the decision whether to fire Pantaleo is up to Police Commissioner James O'Neill, who will decide by Aug. 31 after he receives a report from the administrative judge overseeing Pantaleo's departmental hearing. Potential punishment ranges from loss of vacation days to termination.

Pantaleo's lawyer, Stuart London, said Tuesday that the officer "is gratified that the Justice Department took the time to carefully review the actual evidence in this case rather than the lies and inaccuracies which followed this case from its inception."

In the years since Garner's death, the NYPD has made sweeping changes on how it relates to the communities it serves, ditching a policy of putting rookie officers in higher-crime precincts in favor of a neighborhood policing model that revolves around community officers tasked with getting to know New Yorkers.

De Blasio, who launched his long-shot presidential campaign in May, has boasted on the campaign train of his record in improving police-community relations.

He said Wednesday that "systemic change" in the police department lessens the likelihood of another death like Garner's ever taking place in the city.

"I believe we've taken the kind of steps to avoid such a tragedy," de Blasio said. "That's what a leader has to do."