Van der Sloot, 36, was extradited to Alabama in June from a prison in Peru, where he has been serving a 28-year sentence for murdering another woman in Lima.

He initially pleaded not guilty in the US district court in Birmingham to two federal charges of extortion and fraud, in which he was accused of conspiring to get Holloway’s mother, Beth Holloway, to pay him US$250,000 in 2010 in exchange for his telling her where her daughter’s remains were buried.

Holloway, an 18-year-old from a Birmingham suburb, went missing in 2005 during a high school graduation trip to Aruba, a Dutch territory in the Caribbean.

Eyewitnesses said she was last seen leaving a bar in a car with van der Sloot on the night of her disappearance. While her remains have not been discovered, an Alabama judge declared her legally dead in 2012.

Van der Sloot has reached a plea deal with US prosecutors that requires him to also truthfully disclose what happened to Natalee Holloway, according to John Q Kelly, a lawyer for the Holloway family.

A public defender representing van der Sloot and a spokesman for the US attorney’s office did not respond to questions about a plea deal.

Working with the Federal Bureau of Investigation in a sting operation, Holloway’s family wired a portion of the demanded money to van der Sloot in 2010, but he then provided false information about where Holloway’s remains were buried, prosecutors say.

In 2012, van der Sloot was convicted in Peru after he confessed to beating, strangling, and suffocating Stephany Flores, a 21-year-old Peruvian business student, in May 2010.