A woman who offered a man an orgy and anal sex in exchange for tickets to the baseball World Series - not knowing he was an undercover cop - has gone on trial in America.

Susan Finkelstein was arrested in Philadelphia in October 2008 after she met the undercover officer when he responded to a Craigslist ad she had placed titled 'DESPERATE BLONDE NEEDS WS TIX'.

The ad began: 'Diehard Phillies fan -- gorgeous tall buxom blonde -- in desperate need of two World Series tickets.'

The undercover officer alleges that, after a short chat, she offered him anal sex in exchange for the ticket, saying she had brought lube with her. When the officer said he had a brother, 'Bob', who also had a ticket, he says Finkelstein then offered to have a threesome with the two.

Finkelstein - who is charged with prostitution and criminal attempt - insists she was just leading him on in the hope of getting a better price on the tickets.

Speaking in her defence, Finkelstein's attorney William J. Brennan said: 'If she is in the business of prostitution, is she just open in October?... So she's just open in the Octobers when we have [the Phillies] in the World Series? That business is not open very often.'

Finkelstein did in fact end up going to see the Philadelphia Phillies beat the Tampa Bay Rays to win the World Series - after a local radio station offered her tickets.