A federal judge yesterday refused to reopen a magistrate's decision that Michael Vernon Townley, convicted of plotting the 1976 murder of former Chilean ambassador Orlando Letelier, cannot be extradited to Argentina to face a murder charge there.

At a hearing at U.S. District Court in Alexandria, Judge Albert V. Bryan Jr., agreed with Townley's lawyers that magistrates' decisions on extradition matters cannot be appealed.

The Justice Department, representing Argentina under a 1972 extradition treaty, had asked Bryan to either reconsider the government's request that Townley be extradited, which was rejected last month by U.S. Magistrate W. Harris Grimsley, or order Grimsley to reconsider his decision.

Special Assistant U.S. Attorney Leonie M. Brinkema, at a hearing yesterday, agreed that the government could not appeal Grimsley's decision but said that a request for reconsideration was different.

"Looks like an appeal, acts like an appeal. Seems to me it is an appeal," Bryan told Brinkema about the government's request.

Jeffrey M. Johnson, an attorney representing Townley described the government's move as "unseemly and misguided" and told Bryan "the law doesn't permit it and you shouldn't permit it."

After 30 minutes of argument, Bryan denied the government's request, saying, "I don't think that reconsideration is anything more than an appeal."

Townley, 40, pleaded guilty in 1978 to conspiring to assassinate Letelier, who died with a coworker in a car-bomb explosion on Embassy Row in 1976. Townley testified for the government against other defendants and was granted immunity from further prosecution in return.

In April, Townley was paroled from prison after serving 62 months of a 10-year sentence. He is currently at an undisclosed location under the protection of the U.S. Marshals Service.

Argentina has alleged that Townley was involved in the death of Chilean Gen. Carlos Prats, who died with his wife in a car-bombing in Buenos Aires in 1974. Its request has been linked in press reports to a U.S. request for the return of suspected cocaine dealer in Argentina.

Grimsley ruled last month that key elements of evidence cited by Argentina against Townley had been disclosed by Townley himself under his immunity agreement. Therefore, Grimsley found, the information could not be used to argue for his extradition.

Attorneys on both sides said prosecutors could continue efforts to extradite Townley by filing a new request thus restarting the entire process. Brinkema declined to comment on the government's plans.