Nearly 3,000 veteran cops who flooded the Police Academy 20 years ago as part of the NYPD’s seminal Safe City, Safe Streets program are eligible to retire this month — a loss that threatens to reverse the city’s historic crime drop, sources say.

A new Police Academy class is set to be sworn in this January, but the department is still hemorrhaging experienced street cops faster than it’s replacing them, the sources add.

“They’re scrambling for bodies,’’ one police source said.

The current wave of potential new retirees entered the Police Academy Aug. 30, 1993. They were the first to be hired upon graduation in 1994 under Safe City, Safe Streets.

“They were recruited under Mayor David Dinkins and hit the streets in March 1994, just two months after Mayor Giuliani began his first term, part of a new vanguard seeking to address the crack epidemic roiling the city.”

The program continued to bolster the NYPD’s patrol force for the next five years, adding about 7,000 cops in all and swelling its ranks from 31,000 to more than 38,000.

The department’s strength topped out in 2001 with 40,800 cops.

But those numbers have since steadily fallen to the current level of roughly 35,000 cops, sources said.

And as each successive Safe City, Safe Streets class comes up for retirement, the numbers will fall even more, sources warn.

Of those cops who stay among the rank and file, about 80 percent retire after 20 years with the department, sources said.

While 1,246 recruits were sworn in last month, they won’t make up the difference, insiders say.

City Councilman Peter Vallone, head of the Public Safety Committee, said the NYPD is ignoring its history by not doing more to beef up its numbers now.

“I think people should be extremely worried,” he said.

“Safe City, Safe Streets taught us a lesson, and it’s a lesson that people are forgetting. There doesn’t seem to be any plan to keep up with the attrition.”

“The crime rate has stopped dropping at the level that it has in the past, and certain crimes have been going up, and that’s directly the result of not having enough cops on the street,” Vallone said.

The NYPD declined requests for comment.

City crime has fallen a modest 1.89 percent so far this year, through Aug. 11, largely due to 26 percent fewer murders.

There have been 199 murders so far this year, compared with 269 in the period last year.

But three of the seven major crime categories are inching up this year, with a 0.7 percent increase in rapes over the period last year, a 1.5 percent hike in assaults and a 4.3 percent jump in grand larcenies.

Insiders fear any further decrease in patrol strength — coupled with the recent federal-court decree limiting stop-and-frisks — will be a double whammy for crime fighters.

“The next mayor, whomever it happens to be, will inherit a degraded police force,” said one glum law-enforcement source.

Patrolmen’s Benevolent Association President Patrick Lynch decried the reduction in ranks.

“We’re the only police force in the country that has downsized since Sept. 11.,” he said. “Every other police department in the country talks about becoming more robust while we have shrunk our ranks.”