ALBANY – Actress Allison Mack pleaded guilty Monday to federal charges connected to her longtime involvement in NXIVM, a cult-like self-help group in the Albany area whose leader is accused of treating women as sex slaves.

Mack, 36, best known for her role as Chloe Sullivan in the CW's Smallville, signed a plea agreement late Monday morning in Brooklyn federal court, admitting to two racketeering felonies that could put her behind bars for years when she is sentenced in September.

Mack had been facing seven federal felonies in connection with her role as a high-ranking leader in DOS, a group secretly led by NXIVM co-founder and spiritual leader Keith Raniere that purported to be a women's empowerment sorority.

Federal prosecutors said the DOS group was essentially a sex ring to benefit Raniere, with women known as "slaves" who reported to "masters" who ultimately reported directly to him and were wholly devoted to his teachings.

Mack's plea came the same day jury selection began for the NXIVM trial. Now, three defendants remain, including Raniere and Segram's liquor heiress Clare Bronfman, the group's major funder.

"I believed Keith Raniere's intentions were to help people and I was wrong," Mack said in court, according to The Associated Press.

"I know I can and will be a better person," she said.

Mack accused of recruiting women

Prosecutors say Mack was a co-conspirator, recruiting women to join the master-slave group. She reported directly to Raniere.

The women, some of whom were branded with a logo containing Raniere's initials, were presented to him for sex and forced to follow restrictive diets to adhere to his preferred body type, according to prosecutors.

They were also forced to give up collateral — nude photos, family secrets — in order to join the group. DOS leaders threatened to release the information if the women publicly revealed the group's existence, prosecutors claim.

More:Rochester woman tells all about life with NXIVM's Keith Raniere, her ex

Mack's plea deal Monday had her admit to using the threat of extortion to force lower-level DOS members to give up their personal collateral and forcing a woman (identified only as a Jane Doe) to perform manual labor under threat.

Under the agreement, five charges were dismissed, including three related to sex trafficking.

She faces up to 40 years in prison when she is sentenced Sept. 11, though sentencing guidelines will likely call for less than the maximum.

Trial set to begin for remaining defendants

In recent weeks, federal prosecutors have acknowledged in court that Mack and some of her co-defendants had been engaged in plea negotiations.

Nancy Salzman, NXIVM co-founder and president, pleaded guilty last month to one count of racketeering conspiracy, confessing to stealing email addresses and passwords of NXIVM critics and altering a tape used in a lawsuit against one.

Her daughter, Lauren Salzman, also pleaded guilty to racketeering and racketeering conspiracy last month.

With Mack's expected plea, three defendants remain: Raniere, Bronfman and Kathy Russell, a NXIVM bookkeeper.

Raniere, 58, attended high school in Suffern, Rockland County, before moving to the Albany area to attend the Rensselaer Polytechnic Institute.

He gained a devoted following through NXIVM, which taught expensive self-help classes that were based on Raniere's teachings.

But Raniere's critics — including former girlfriend Toni Natalie of the Rochester area, who has spoken out publicly against him for years — have long accused NXIVM of operating like a cult, aggressively suing former members who went on to criticize the group.

Federal prosecutors got involved after Sarah Edmondson, an actress from Vancouver, went public in an account inThe New York Timeswith news that women in DOS, the secret sorority, had been branded on their pubic region with Raniere's initials.

The account also detailed Dynasty star Catherine Oxenberg's fight to rescue her daughter from the group.

More:NXIVM co-founder Nancy Salzman pleads guilty in case of alleged cult

More:The charges against NXIVM's Keith Raniere, Allison Mack and Clare Bronfman, explained

JCAMPBELL1@gannett.com