Updated

A 22-year-old U.S. Navy sailor pleaded guilty Thursday to four counts of attempted espionage for trying to sell classified documents to someone he believed was a Chinese intelligence officer.

Petty Officer 2nd Class Bryan Minkyu Martin of Mexico, N.Y., faces a maximum sentence of life in prison.

At a court martial in Norfolk, Martin said Thursday that he accepted $11,500 from an undercover FBI agent known to him only as "Mr. Lee" in exchange for information, documents, photographs and images that were classified as secret or top secret. The documents involved naval operations and intelligence assessments, with at least some of those related to military operations in Afghanistan and Iraq. Authorities say the documents were delivered to the agent in November and December over the course of three weeks before Martin was arrested at his final meeting with him, in which he received $8,000 in cash.

Martin said it was several days after his arrest before he learned he had been negotiating with an undercover FBI agent.

Martin is an intelligence specialist who was stationed at Fort Bragg in North Carolina at the time, preparing for a deployment to Afghanistan. He worked at the base's Joint Special Operations Command and downloaded and printed documents from his desktop computer while at work, sometimes walking out with them folded up in his pants pocket.

He said he wanted to sell the documents to the Chinese because he believed they would pay the most for them. Prosecutors declined to say how Martin made the initial contact that ultimately got him in touch with the undercover agent.

Martin said he had spoken with the undercover agent by telephone, but had never seen him until their first meeting in a hotel lobby, saying he identified "Mr. Lee" because he was reading a Chinese newspaper. The undercover agent never showed any identification to prove he worked for the Chinese government and Martin said he was initially cautious that he might not be legitimate. Martin offered to travel to Beijing, but was told that wouldn't be a good idea.

He earned $500 at the first meeting for verbally sharing classified information he gleaned while training at the Defense Intelligence Agency and at Fort Bragg, which he was stationed at beginning in September of 2010. Martin said he had access to a special operations information system terminal at work in North Carolina.

Martin said he had three other meetings with the undercover agent at various hotels in Spring Lake, N.C. At each of those subsequent meetings, he signed receipts for payment of the documents. The information he downloaded and printed out included

Martin also pleaded guilty to seven charges levied against him for mishandling classified documents. Prosecutors withdrew four other related charges involving classified documents based on a pre-trial agreement.

His sentencing hearing is scheduled to last through Friday. Prosecutors are expected to play three hours of videotape recorded by federal agents. Martin's parents, a psychologist and an intelligence specialist are also expected to testify.

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Brock Vergakis can be reached at www.twitter.com/BrockVergakis