A 22-year-old who tried to cut into a long Brooklyn gas line by flashing a badge and claiming to be a federal agent was charged with impersonation, sources said.

Milan Nus tried the ruse at the BP on Ocean Avenue in Sheepshead Bay around noon Thursday, but cops weren’t fooled by the phony shield, according to law enforcement sources.

Nus was arrested and arraigned yesterday on an impersonation charge, records show.