A former FBI intelligence analyst admitted that for five years he passed classified information gleaned from White House and FBI computers to conspirators he said were trying to overthrow Philippine President Gloria Macapagal Arroyo.

Leandro Aragoncillo, 47, a naturalized U.S. citizen who was born in the Philippines, pleaded guilty Thursday to charges in a four-count indictment. The most serious charge, conspiracy to transmit national defense information, can carry the death penalty. But under a plea agreement, Aragoncillo faces 15 to 20 years in prison.

"It was information that had the potential to compromise U.S. national security," said U.S. Attorney Christopher J. Christie.

Aragoncillo, a former Marine, worked as a military aide to vice presidents Al Gore and Dick Cheney starting in 1999. After retiring from the Marines, he became a civilian employee of the FBI, working at Fort Monmouth in central New Jersey.

He was arrested in September, along with Michael Ray Aquino, a former Philippine police official who is accused of passing information from Aragoncillo about Filipino leaders to current and former political officials in the Philippines.

Aragoncillo did not identify the officials. But according to documents filed in U.S. District Court in Newark, they included former Philippine President Joseph Estrada, opposition Sen. Panfilo Lacson and former House Speaker Arnulfo Fuentebella. Estrada last week denied suggestions by U.S. prosecutors that he conspired with Aragoncillo to overthrow Arroyo.

Aquino, a Philippine national living in New York, pleaded not guilty in October to an indictment charging conspiracy and acting as an unregistered foreign agent.

His lawyer, Mark A. Berman, contacted after Thursday's hearing, said Aquino did not know that the material he received from Aragoncillo was classified.

Under questioning by Assistant U.S. Attorney Karl H. Buch, Aragoncillo admitted taking dozens of documents from White House and FBI computers and passing them by hand, e-mail, fax and telephone.

The conspirators used code words to refer to various people, including calling President Arroyo "The Penguin," Aragoncillo admitted.

One question asked if he knew that a document he took in February 2005 from an FBI computer at Fort Monmouth contained "national defense information relating to terrorist threats to U.S. military personnel in the Philippines."

Aragoncillo answered, "Yes, sir."

Afterward, Aragoncillo's public defender, Chester M. Keller, said his client never intended to harm the United States and never received any money for his efforts.

"It was his sole intention to help the people of the Philippines," Keller said.