WASHINGTON – A Duke University official has been arrested and charged with offering his adopted five-year-old son for sex.

Frank Lombard, the school’s associate director of the Center for Health Policy, was arrested after an Internet sting, according to the FBI’s Washington field office and the city’s police department.

According to an affidavit by DC Police Det. Timothy Palchak, an unnamed informant facing charges in his own child sex case led authorities to Lombard.

Authorities said that Lombard tried to persuade a person — whom he did not know was a police officer — to travel to North Carolina to have sex with Lombard’s child.

The detective’s affidavit charges Lombard identified himself online as “perv dad for fun,” and says that in an online chat with the detective, Lombard said he had sexually molested his son, whom he adopted as an infant.

The court papers say Lombard also invited the undercover detective to North Carolina to have sex with the young boy, and even suggested which hotel he should use.

Lombard was charged in federal court in Washington with attempting to induce someone to cross state lines to engage in sex with a child. If convicted, he could face a maximum sentence of 20 years in prison.

Lombard’s lawyer did not immediately return a call seeking comment.

Michael Schoenfeld, vice president for public affairs at Duke, said Lombard has been employed with Duke University since 1999. He is now on unpaid administrative leave.

“Duke is cooperating with the investigation,” Schoenfeld said. He said the university was notified of the incident after Lombard was arrested.