Manhattan US Attorney Jay Clayton on Sunday said he wants to root out more crime in housing projects — and already warned Mayor-elect Zohran Mamdani not to undermine the NYPD’s “preventing policing.’’

The President Trump appointee said US authorities and prosecutors in general are focusing more on local crime and corruption because federal laws are tougher than regional criminal-justice systems such as New York City’s to put away the bad guys.

“[During] certain weeks, we are positioning our attorneys in precincts around the city where we have the most violent, gun-toting criminals,” Clayton said Sunday on 77 WABC’s the “Cats Roundtable” radio program. “We charge [suspects] federally if we can because there’s a greater likelihood of detention.

“And if we’re able to prove the case, they’re going to get and serve longer sentences,” the US attorney said. “That’s what New York wants. The New York people, they want gun-toting criminals off our street.”

Clayton said he advised the lefty Mamdani to let the NYPD continue to do one of the things it does best — “preventative policing — by preserving specialized department units such as the Strategic Response Group that handles counter-terrorism, protests and riots.

“The New York Police Department is the greatest police department in the world. It’s not even close [to others],” Clayton said. “[The NYPD’s] efforts in preventive policing … are so far ahead of the other big city police departments.

“To get rid of preventive policing would be a huge mistake. … You’re not treating people better by pulling back on the police. You actually create more violence scenarios for everyone.”

Mamdani has called for disbanding the SRG.

Clayton said he’s also looking for his office to help take down other open-air drug markets in the city after the recent crackdown in Washington Square Park — as well as root out gang violence, gun-trafficking and corruption, including in local public housing projects.

Clayton discussed the recent federal indictment of 19 suspected narc-dealers operating in Washington Square Park. The feds’ clean-up effort was done in concert with the Drug Enforcement Agency and the NYPD.

“I’m happy to say, with the New York Police Department’s continuing vigilance there, that Washington Square Park is now a park and not a drug den,” Clayton told host John Catsimatidis.

Residents and elected officials have complained about other open-air drug markets, such as The Hub on Third Avenue in the South Bronx and in East Harlem.

“We’re looking for other places around the city … public housing, parks, well-known thoroughfares where that type of operation should be brought. … It’s a quality-of-life matter,” Clayton said.

“You can’t have safety if you have open-air drug dealing.”

Clayton, who Trump appointed US attorney for the Southern District encompassing Manhattan, The Bronx and the city’s northern suburbs, also said he’s trying to clean up corruption and violence at the New York City Housing Authority complexes.

He noted that 70 NYCHA employees who were arrested and charged last year in a massive corruption case have pleaded guilty or were convicted of bribery, fraud or extortion offenses. The initial bust last year was the largest single-day bribery takedown in the Justice Department’s history.

“That’s another area where the federal government is stepping in. We’re trying to stamp out corruption in the Housing Authority,” he said of the city’s $13 billion agency.

He also complained there’s too much junk justice with the state’s cashless bail laws, lax judges and local district attorneys who put criminals back out on the streets.

“If somebody’s going to get a sentence of one year or two years for a violent crime, they are very unlikely to cooperate and help prosecutors and law enforcement to find the other participants in the violent crime,” Clayton said.

“If they’re facing 10 years, they are likely to help us [to] get more criminals off the streets. There are knock-on effects to these very light sentences that are truly problematic for public safety.

“All New Yorkers should ask themselves, ‘Do we want judges who are worried about public safety?’ I think New Yorkers do. And I think our officials, including the new mayor, should hear from New Yorkers that we want a focus on public safety, and career violent criminals should not be on our streets. … We do not want to go back to where things were in 1975.”