Police are on the hunt for a man they say impersonated a cop, then kidnapped and sexually assaulted a teenage boy in Sunset Park.

Cops say the suspect picked up the 15-year-old boy on the R platform at 53rd Street and 4th Avenue.

According to police, the boy threw an empty bag of chips on to the platform and was then approached by the man. The victim told police the suspect was dressed in civilian attire and flashed what looked like a police badge.

Police say the suspect drove the boy to a location near 92nd Street and Dahlgren Place and sexually assaulted him. The suspect then dropped the teen off near 38th Street and 4th Avenue.

The suspect is described to be a white male, about 5'8" and in his late 40s with a gray mustache, bald head and a mole under the left side of his lip.