A Bronx cop was clinging to life Thursday after a street confrontation stemming from a thrown water balloon.

Ernesto Rodriguez, 43, angry about his car being hit by the balloon, approached a group of teens and at least one young man. Someone in the group “sucker-punched” him, police sources said.

The cop fell and cracked his head on the sidewalk.

Rodriguez, an instructor at the Police Academy, was in critical condition yesterday in the intensive care unit at St. Barnabas Hospital.

Keith McNeil, 20, surrendered last night and was charged with misdemeanor assault.

Rodriguez was off duty, driving with his 7-year-old son near his home around 4:40 p.m. Wednesday when a youngster on the street threw a water balloon at his car.

He pulled over at the corner of 181st St. and Tiebout Ave., got out and walked up to a group of youths on the corner.

That’s when he was punched and fell on his head, according to police sources.

Rodriguez underwent brain surgery Wednesday night as doctors worked to relieve the swelling in his brain

“He’s still holding his own,” said one police source.

“Something like this, he could be out and about in a week – or he could be dead.”

NYPD Commissioner Raymond Kelly visited the officer’s family at the hospital.

(Source: NY Daily News)