U.S. immigration authorities have notified Luis Posada Carriles that they are not ready to turn him loose, despite a magistrate's ruling in Texas.

BY FRANCES ROBLES

Calling him an ''unrepentant criminal and admitted mastermind of terrorist plots,'' federal authorities have decided to prolong the detention of anti-Castro militant Luis Posada Carriles, despite a judge's recommendation that he be freed.

U.S. Immigration and Customs and Enforcement notified Posada on Thursday, saying the agency is debating with the State Department over whether they can continue holding him on grounds that his release would have serious foreign policy consequences, ICE said in a statement Friday.

''ICE's determination not to release Posada at this time is based on considerations such as flight risk, danger to the community, and his failure to demonstrate that there is no significant likelihood of removal in the reasonably foreseeable future,'' the statement said.

Posada, 78, is a former CIA operative who dedicated his life to plots against Cuban leader Fidel Castro. He was the prime suspect in the 1976 bombing of a Cubana de Aviación flight that killed 73 people, and he admitted planning a string of Havana hotel bombings in the late 1990s.

A Venezuelan court acquitted Posada of the bombing, and he escaped while prosecutors appealed the verdict.

A fugitive for more than a decade, he was arrested in Panama on yet another scheme to assassinate Castro in 2000. Pardoned, he arrived in South Florida last year. Posada has been held on immigration charges in El Paso, while the Cuban government clamors for his extradition.

The case has put the United States in the precarious position of being perceived to harbor a terrorist. Although immigration officials characterize him as a dangerous criminal, Posada has not been charged with any crime here. Authorities have been reluctant to hand him over to Cuba or Venezuela, which both seek him in connection with the airline bombing.

An immigration judge refused to release Posada to either Cuba or Venezuela on the argument that he could be tortured there. He sued ICE in federal court when the agency refused his request to be released.

In El Paso, U.S. Magistrate Norbert Garney wrote last month that the agency should put Posada under supervised release because the federal government had failed to find a country willing to take him. Posada could be held if the U.S. government had officially classified him a terrorist, which it has not done.

Posada's attorneys argue that U.S. Supreme Court precedents don't allow authorities to indefinitely hold people on immigration charges when they can't be deported. Lawyer Eduardo Soto did not return calls for comment Friday.

Friday was the 30th anniversary of the Cubana de Aviación bombing, commemorated by a procession to the Colón cemetery in Havana.

''It is sad to see all these children, grandchildren, parents, without their loved ones today,'' Ondina Pérez, whose brother piloted the doomed aircraft, told the Associated Press.

Meanwhile, the National Security Archive, a research institute and library at George Washington University in Washington, D.C., posted newly declassified documents that detail Posada's involvement in the bombing.

A deposition by an investigative officer shows one of the arrested bomber's first telephone calls was to Posada's office. Other memos show how the highest levels of the U.S. government grappled with news of Posada's involvement.

The documents revealed that a tube of Colgate toothpaste had been used to disguise plastic explosives that were set off with a ''pencil-type'' detonator on a timer, the National Security Archive said.

The Cuban government has long accused the CIA of masterminding the attack.

''The Cuban government believes once a CIA agent, always a CIA agent,'' said the archive's Peter Kornbluh. ``My position is the CIA recruited Posada, trained and financed him and then unleashed him. He is their most famous Frankensteinian monster.''