Steven J. Devlin, 50, who was a vice provost at the university, was arrested in July for allegedly soliciting sex from what he believed to be a mother and two daughters under age 10. Devlin was, in fact, chatting online with a Delaware County detective.

Under the terms of the plea agreement, prosecutors seek a three- to six-year prison sentence, said Devlin's attorney, Arthur T. Donato Jr. The maximum penalty is 20 years in prison and a $25,000 fine.

A sentencing hearing is scheduled for Aug. 11.

Lehigh University put Devlin on administrative leave after his arrest. His employment has since been terminated.

Last May, Devlin logged onto AOL under the screen name Phillyguy05 and started a relationship with a female county detective posing as a 32-year-old woman with two daughters ages 7 and 9, according to a police affidavit.

Using instant messages, Devlin told the detective that he and his wife grew up in an "open-minded" lifestyle and they began "preparing" their own two daughters at ages 10 and 12, according to the criminal complaint.

Over the course of several online conversations conducted at his Lehigh office, Devlin suggested that "we should try to find a way to do more than chat online," according to the criminal complaint. Devlin detailed explicit sexual activity that would occur if they met and specifically asked that the girls be included, according to the complaint.

Devlin had similar communication in June with another female detective posing online as the mother of two daughters ages 11 and 14, according to the affidavit.

Devlin was arrested July 10 at a planned meeting spot in Morton.

Devlin began working at Lehigh in March 2003, the university said after he was arrested. Before that, he worked for nine years at the University of Pennsylvania in several positions, including as director of the Boettner Center of Financial Gerontology in the School of Social Work and as associate director of institutional research.

Devlin has been monitored electronically since he posted 10 percent of $250,000 bail after his arrest.