Daniel Rosen was arrested at his home in Washington just after noon and is being held in the city's jail on suspicion of use of a communications device to solicit a juvenile, said Lucy Caldwell, spokeswoman for the Fairfax County Police Department.
Caldwell said Rosen's arrest was the result of an online exchange between him and detectives in her agency's child exploitation unit.
He is expected to be extradited to the Fairfax County Jail soon.
According to his LinkedIn profile, Rosen, 44, is the director of counter-terrorism programs and policy for the State Department. Police said they had notified the State Department of his arrest.
"We are aware that a State Department employee has been arrested and charges have been issued," State Department spokeswoman Jen Psaki said.
Psaki declined to name the employee or the charges, citing privacy reasons.
"His security clearance will be suspended, and he will be put on administrative leave while this proceeds to its end through any judicial process," Psaki said.
It is unclear whether Rosen is alleged to have used personal or State Department-issued devices. Police did not say whether any search warrants had been served at his home or work.
Rosen attended UCLA, graduating with a degree in political science and international relations in 1993, according to his LinkedIn profile and his biography from a 2012 counter-terrorism seminar at the Potomac Institute for Policy Studies.
He received a master's degree in law and diplomacy from Tufts University in 1997.
FOR THE RECORD
Feb. 24, 10:07 p.m.: An earlier version of this article stated that Daniel Rosen received a law degree from Tufts University. According to his LinkedIn page and a biography, he received a master of arts in law and diplomacy from the Tufts Fletcher School of Law and Diplomacy.
According to the biography, he is responsible for policy and strategic planning in the counter-terrorism bureau, and previously spent two years as a senior advisor with the State Department's Office of the Coordinator for Counterterrorism.