A man who allegedly posed as a cop to extort free sex from a prostitute was arrested Wednesday.

Ernesto Taype Miranda, 26, met the 24-year-old woman at her West 55th Street apartment on Feb. 9, having agreed to pay her $500, police sources said.

But he pulled a fast one and allegedly flashed a US Marshals badge, threatening to book her unless she had sex with him.

Miranda spent two hours with the call girl before refusing to pay the rate robbed $160, cops said.

The prostitute then got a call from Miranda two days later, allegedly demanding weekly payments of $500 or sex — “her choice” — in exchange for his silence.

Calling his bluff, she arranged another meeting, then reported Miranda to police.

A sting was in place when he arrived at her place Wednesday afternoon, and Miranda — convicted in 2009 of police impersonation — was arrestedtaken down by an NYPD apprehension team, cops said.

A phony U.S Marshal shield and a BB gun in a shoulder holster were found in his possession, cops said.

Miranda was charged with rape, robbery, burglary, unlawful imprisonment, criminal possession of a weapon, and impersonation of an officer.

He has prior convictions from 2009 including other incidents of police impersonation.

The victim will not be charged, sources said.