"Smallville" actress Allison Mack on Monday pleaded guilty to blackmailing two women as part of an alleged New York sex cult that prosecutors called a racketeering operation that carried out sex trafficking and other crimes.

Mack, 36, entered her plea to racketeering and conspiracy charges before U.S. District Judge Nicholas Garaufis in federal court in Brooklyn, New York, admitting that she coerced the two unnamed women into performing services by threatening to release damaging information about them.

Fighting back tears, Mack said she had joined the organization, led by self-described spiritual guide Keith Raniere, a decade ago to find purpose in life.

"Through it all, I believed that Keith Raniere's intentions were to help people," she said. "I was wrong. I now realize that I and others engaged in criminal conduct."

There was no mention at the plea hearing of any agreement by Mack to cooperate with prosecutors against Raniere, who is expected to go on trial later this month. Mack's lawyers declined to provide any further details about her plea deal.

Raniere, 58, was arrested on sex trafficking charges in March 2018, and is being held without bail. Mack was arrested the following month.

Prosecutors accused Raniere of running a cult-like secret society within his organization, Nxivm (pronounced "Nexium"), in which women were branded with his initials, put on extremely restrictive diets and forced to have sex with him.

Last month, prosecutors unsealed new charges accusing Raniere of sexually exploiting a minor and coercing her to produce child pornography.

Raniere has pleaded not guilty. Marc Agnifilo, one of his lawyers, declined to comment on the case after Monday's hearing. Agnifilo has previously said that his client's sexual encounters with women in the organization were consensual, and denied the child pornography charges.

Nxivm on its website calls itself "a community guided by humanitarian principles that seek to empower people and answer important questions about what it means to be human." The website now carries a message saying that all "enrollment, curriculum and events" are canceled "until further notice," adding that "we continue to believe in the value and importance of our work."

Two other people charged in the case, former Nxivm president Nancy Salzman and her daughter Lauren Salzman, previously pleaded guilty.

Also charged alongside Raniere are Seagram liquor heiress Clare Bronfman and Nxivm member Kathy Russell, who have pleaded not guilty.

"Smallville," a television series that ran from 2001 to 2011, featured a young Clark Kent before he became famous as Superman. Mack played Chloe Sullivan, a close friend of the future Superman whose romantic feelings were not reciprocated.