WASHINGTON — A scientist and his wife who both once worked at Los Alamos National Laboratory were arrested Friday after an FBI sting operation and charged with conspiring to help develop a nuclear weapon for Venezuela.

After their arrest, the two appeared in federal court in Albuquerque, N.M.

They were accused of dealing with an FBI undercover agent posing as a Venezuelan agent. The government did not allege that Venezuela or anyone working for it sought U.S. secrets.

The pair were indicted for allegedly communicating classified nuclear weapons data to a person they believed to be a Venezuelan government official.

Accused in a 22-count indictment are Pedro Leonardo Mascheroni, 75, a naturalized U.S. citizen from Argentina, and Marjorie Roxby Mascheroni, 67, a U.S. citizen. Both were formerly contract employees at Los Alamos.

According to the indictment, Pedro Mascheroni told an undercover agent he could help Venezuela develop a nuclear bomb within 10 years and that under his program, Venezuela would use a secret, underground nuclear reactor to produce and enrich plutonium, and an open, aboveground reactor to produce nuclear energy.

In July 2008, the FBI agent provided Mascheroni with 12 questions purportedly from Venezuelan military and scientific personnel.

According to the criminal charges, Mascheroni delivered to a post office box in November 2008 a disk with a coded 132-page document on it that contained “restricted data” related to nuclear weapons. Written by Mascheroni and edited by his wife, the document was entitled “A Deterrence Program for Venezuela” and it laid out Mascheroni’s nuclear weapons development program for Venezuela.

Mascheroni stated that the information he was providing was worth millions of dollars, and that his fee for producing the document was $793,000, the indictment alleges.

Earlier in the investigation, Mascheroni allegedly asked the FBI agent about obtaining Venezuelan citizenship.

He told the undercover agent he should be addressed as “Luke,” and that he would set up an e-mail account solely to communicate with the undercover agent, according to the indictment.

Mascheroni used the account to communicate with the agent and to arrange for deliveries of materials at the post office box used as a dead-drop location.

If convicted, the couple face up to life in prison.