A Utah trucker accused of keeping women as sex slaves in his semi-trailer as he drove across the country struck a plea deal with federal prosecutors Thursday, days before his trial was set to begin.

Timothy Jay Vafeades was charged with luring two women ages 18 and 19 to his truck, then forcibly altering their appearances and grinding down their teeth while holding them prisoner for months. Prosecutors say he had four other victims in the decades before his 2014 arrest, and their stories would have been evidence in the trial even though the cases are too old for criminal charges.

He now faces up to 20 years in prison under the terms of the deal. He pleaded guilty to two counts of transporting for illegal sexual activity and two kidnapping charges will be dropped in exchange. Sentencing is set for November.

Prosecutors hope the plea is a step toward closure for the victims, Assistant U.S. Attorney Trina Higgins said. Defense attorneys declined to comment.

Vafeades, 56, was accused of attacking the 19-year-old when she said she wanted to leave after working on his truck known as "Twilight Express" in 2013. He trapped her and sexually assaulted repeatedly for six months, forcing her to wear a fake set of teeth while he wore one with vampire fangs, authorities said. Vafeades was arrested after officers at a Minnesota weigh station noticed bruises on the woman's face and discovered an old restraining order barring Vafeades from contacting her, according to charging documents.

After his arrest, a second woman went to authorities to report she had been held captive in Vafeades' truck, according to the warrant.

The 18-year-old woman said Vafeades kept her with him for about three months through threats and violence, forcing her to have sex with him nearly every day, calling her his slave, authorities said.

Vafeades' lawyers have said the Minnesota arrest was shouldn't have happened because the protective order was no longer valid. Attorney Vanessa Ramos has asked a judge to bar the evidence seized from his truck, but the judge decided the stop was valid.

Vafeades had four additional victims in the two decades before his arrest, prosecutors allege. He met one woman when he was a hospice patient and married her, but started assaulting her after she agreed to go to Utah with him and continued until she escaped about six months later, according to court documents.

He met another woman at a retail store and invited her to join him in his truck for a week in 2005, but then held her on board for about three months before she got away, court documents state. Vafeades also assaulted women he met at a college and online, authorities said. No charges were filed in those cases because the statute of limitations was up, but prosecutors said their stories showed preparation, planning and intent.

Vafeades pleaded guilty in May transporting child pornography and a second child pornography count was dropped.