The Bush administration on Friday rejected Venezuela's request for the arrest of Cuban exile Luis Posada Carriles so he could be returned to the South American country for trial.
Venezuelan authorities want Posada, a foe of Cuban President Fidel Castro and a former CIA operative, in connection with the 1976 bombing of a Cuban passenger plane that killed 73 people.
Posada was acquitted twice in the bombing by courts in Venezuela, but he escaped from a Caracas jail in 1985 while an appeal was pending.
Relations have been strained recently between the United States and the government of leftist Venezuelan President Hugo Chavez, Cuba's closest ally and a critic of President Bush.
This month, Venezuela asked the United States to arrest Posada as an initial step toward extradition.
Days after the request was received, U.S. authorities detained Posada on their own and charged him with illegal entry into the United States.
Posada, who entered the United States secretly in March, is scheduled to appear before an immigration judge on June 13.
The Department of Justice ruled that the Venezuelan arrest request "did not include any statement of the evidence against the accused required for the issuance of an arrest warrant in the United States," an administration official said.
The official, speaking on condition of anonymity, said the Venezuelan request made no mention of Posada's acquittals.
State Department officials questioned whether Venezuela deliberately provided too little documentation to support its request because its ultimate goal was to embarrass the U.S. government.
If Posada is not brought to justice, other countries could cite his case in considering potential U.S. requests for anti-terrorism cooperation, said Cuba expert Philip Peters of the Lexington Institute, a think tank in Arlington, Va.
On the CIA payroll for years, Posada participated in the failed CIA-backed Bay of Pigs invasion of Cuba in 1961. He is a hero to many hard-line exile Cubans in Florida who have supported Bush.
CIA and FBI files show that U.S. investigators believed Posada was involved in the airliner plot.
Posada told the New York Times he was behind the 1997 bombings of Havana hotels that killed an Italian and wounded others.