The off-duty NYPD cop stabbed in a mugging revealed Tuesday that he fought back as his attackers grabbed the gold chain his mom gave  him — adding the thugs didn’t care when he told them he was police.

“I almost died,’’ said Detective Jose Mercedes, speaking for the first time since the bloody Oct. 2 assault by two accused illegal migrants, to reporters at his police union’s headquarters in Manhattan.

“I told them in English, I told them in Spanish that I was a police officer,” he said. “They didn’t care.”

The 10-year NYPD veteran — with his left arm still in a cast and stitches and scars visible on his right arm — described how he chased his attackers for five blocks while profusely bleeding before collapsing on the sidewalk.

Mercedes was assaulted in the middle of the day while cleaning out his car by two men riding an e-bike, according to officials.

The violent duo stabbed Mercedes in the neck, arm and leg 10 times and snatched his gold chain from his neck and fleeing the scene.

The stolen jewelry was a sentimental gift from Mercedes’ mother, he said.

The suspects fled but were caught days later hiding in a basement in Massachusetts.

They were identified as  D’Angelo Caraballo, a 25-year-old illegal immigrant from the Dominican Republic, and 24-year-old Sneinder Mejia, who also was in the country illegally from the DR, according to the NYPD.

Both had prior arrest records in New York City but were dumped back on the street because of local soft-on-crime laws, officials said.

Mercedes — asked Tuesday about his own Dominican descent and the immigration and criminal histories involving his accused attackers  — deflected and spoke instead about how he has dedicated his career to investigating crime.

But DEA President Scott Munro, who stood alongside the wounded detective at the press conference, had some choice words.

“These perpetrators — they’re illegal. They need to do 25 years to life,” Munro seethed.

“They picked on this giant here. Well, guess what? This giant chased them five blocks, bleeding.”

Mercedes reflected on the moments after the attack when he realized how much blood he was losing — but said he had to keep his wits about him because he was so familiar with the work that goes into solving these cases and wanted to do his part in helping investigators.

“I realized I was bleeding a lot. I had lost a lot of blood, and as I sat down, I thought about other cases that I’ve investigated, and I thought about what happens when you lose a significant amount of blood, and I just wanted to stop moving so that I don’t lose more blood,’’ he said.

“I wanted to provide the 911, which has as much information as possible, so that I could get help from EMS, from the police and provide the best description that I was trained to provide on the direction of flight.”

Mercedes  expressing his gratitude for the civilians and first responders who helped him survive this near-death experience.

“All I really want to do is say thank you to all those people that are assisting me and allowing me to stand today,” he said.

-Additional reporting by Amanda Woods