A woman accused of keeping an Indonesian nanny as a virtual slave for four years pleaded guilty Tuesday to a federal charge of harboring an illegal immigrant.

Sarah Khonaizan, 35, faces a sentence ranging from probation to a year in prison and a fine of up to $20,000, attorneys said. In exchange for her guilty plea, prosecutors dropped charges of forced labor and document servitude.

Prosecutors and FBI agents accused Khonaizan and her husband, Homaidan Al-Turki, both of whom are Saudi Arabian, of hiding the woman's passport and forcing her to cook, clean and care for their five children in their suburban Aurora home.

She slept on a mattress on the basement floor and was paid less than $2 a day, an FBI affidavit said.

State prosecutors also alleged that Al-Turki sexually abused the woman repeatedly. The Associated Press is not identifying her because of the sexual assault allegations.

Al-Turki's case is still pending. He faces federal charges of forced labor, document servitude and harboring an illegal immigrant and state charges of sexual assault, kidnapping, false imprisonment, extortion and theft.

Attorneys made no mention of Al-Turki's case Tuesday, and it was not clear whether Khonaizan's plea agreement requires her to cooperate with prosecutors.

U.S. District Judge Walker Miller said he wanted to review a presentencing report before deciding whether to accept her plea. Defense attorney Forrest Lewis said that was not unusual.

Lewis said Khonaizan's concerns about her children prompted her to accept the plea deal.

"Bringing it to a conclusion in a way that allows the family to get back to normal and for her to care for her children was a main motivation," he said.

Lewis said Khonaizan planned to voluntarily return to Saudi Arabia after completing her sentence.

Al-Turki, a linguist, worked at a Denver publishing and translating company.