NEW YORK (AP) _ A ruthless former aide to deposed Panamanian leader Manuel Noriega has planted his own men in the new Panamanian security force to destabilize the U.S.-backed government, according to a newspaper report.

The report in Sunday's editions of New York Newsday quotes U.S. intelligence officers who debriefed Noriega loyalists after the Dec. 20, 1989, U.S. invasion of Panama.

Their information - contained in classified U.S. Army documents obtained by the newspaper - is fueling concern in Washington that Panamanian President Guillermo Endara has been unable to establish full control of the nation, the newspaper said.

Panamanian officials have filed a $6.5 billion lawsuit against Noriega, who is in a federal prison outside Miami awaiting trial on drug conspiracy charges.

The suit includes a report that Noriega has sent coded messages to his supporters in which he discussed how to destabilize the new government, according to the newspaper.

Suspicions about a potential insurgency in Panama focus on Capt. Asuncion Eliezer Gaitan, the paper said. He is a former Noriega aide who headed a Cuban-supported secret intelligence operation undetected by U.S. officials before the Dec. 20 U.S. invasion, Newsday said, quoting the intelligence documents.

Lt. Col. Nivaldo Madrinan, chief of military intelligence under Noriega, told debriefers Gaitan had his people in the operation, according to Newsday.

Jaime Simmonds, former manager of the Panamanian government federal Credit Union, told the U.S. intelligence officials Gaitan planned to go to Libya and return to Panama with an organization backing up a subversive movement. The plan, according to Simmonds, included monetary assistance from Nicaragua, Newsday says.

Gaitan took refuge in the Vatican Embassy after the U.S. invasion and his current whereabouts are unknown. He was known as a ruthless soldier believed to have assassinated members of an abortive coup against Noriega on Oct. 3, 1989, Newsday said.

The classified U.S. documents, including more than 100 interviews with members of the former Noriega regime, were prepared by the Joint Debriefing Center operated by the U.S. Army's 470th Military Intelligence Brigade, the newspaper said.