A Harlem man risked his life to save an FIT student from the clutches of a violent sexual predator who slammed her head against the icy pavement while trying to rape her, the Post has learned.

Dale Green, 46, sprang into action when he heard the blood-curdling screams of the petite 19-year-old who had just paid for a cab ride after a night of partying with friends.

After the victim stepped out from the taxi, convicted rapist Demetrius Edwards, 34, emerged from the darkness and pounced on the petite teen from behind, Green said.

“I kept hearing, ‘Please no! God no! F-ing no! Don’t do this! Don’t do this!” Green told the Post. “I had been watching the Olympics. I thought it was a lovers’ quarrel, a squabble outside but they didn’t pass by.

Green got up to go to the bathroom and looked out the window.

“I saw this guy pick this Asian girl up and put her on the ground between two cars,” he said. “I can’t believe somebody tried to rape somebody in that spot. It’s right out in the open. She was saying ‘No, no, take my keys.’ It seemed like he was trying to hit her really hard, so I started dialing 911.”

While on the phone, he opened the window and talked to the victim, asking: “Are you OK?”

“No! He’s trying to rape me,” the woman cried out.

Green told the victim to stay put while he ran for the door and gave 9-1-1 operators a crystal clear description of the attacker, down to his lined cap with flaps on it.

“He chased the perp right toward the police,” a law enforcement source said. “His description of the suspect and his direction of travel, toward the Madison Avenue Bridge is really what helped us get him.”

Green also looked for the victim, who had run to safety.

Cops Edwards allegedly trying to flee to the Bronx. After he was cuffed, officers brought both the victim and Green to identify the suspect from a patrol car.

Edwards was charged with attempted rape. He has been arrested for three prior sex attacks – in 1998, 1999 and 2001. The first two times, he pleaded guilty to sexual abuse and was sentenced to five years’ probation, law enforcement sources said.

The last time, he pleaded and served three years in prison before being paroled and ordered to register for the rest of his life as a level 3 sex offender, sources added. Level 3 is reserved for the state’s most dangerous offenders and the registry shows he used a firearm, choked the victim and threatened her during the rape.