Confessed assassin Michael Vernon Townley admitted in U.S. District Court yesterday that he lied to a Chilean military investigatory and gave a false "proclamation" to the leading Chilean newspaper that he had nothing to do with the 1976 killing of Orlando Letelier.

Townley, the government's main witness against two anti-Castro Cubans charged in connection with the Letelier assassination, said, however, that his lies were part of a cover-up ordered by Juan Manuel Contreras Sepulveda, then the head of the Chilean secret police, once known as DINA.

The government contends that Townley, following DINA orders, recruited the Cubans to carry out the assassination of Letelier, the former Chilean ambassador, who was killed in a car bomb explosion on Embassy Row in September 1976. A young associate, Ronni Karpen Moffitt, was also killed in the blast. The defendants, Alvin Ross Diaz and Guillermo Novo Sampol, are charged with murder and conspiracy. Their convictions on those charges in 1979 were overturned by the appeals court.

The defense says it will prove that Townley and DINA alone plotted to kill Letelier, an outspoken critic of the military regime of Augusto Pinochet, and decided to put the blame on the Cubans.

The defense yesterday used agreements between Chilean officials, Townley and U.S. officials to try to lsupport the argument that Townley's cooperation in the prosecution, and the scheme to make the Cubans the "scapegoats" for the murders, was plotted out by DINA officials.

Defense lawyer Lawrence A. Dubin asked Townley yesterday if the Chilean military investigator once told him that the only way to save Chile from the political pressure that followed the Letelier murder was to "throw some Christians to the lions of public opinion."

Townley denied that such a statement had been made and said that he had been told to tell the truth and let the case be resolved one way or another in the judicial system. Dubin did not identify the source of the remark.

Townley, an American-born former DINA agent, was expelled by Chile in April 1978, turned over to U.S. law enforcement authorities and eventually pleaded guilty to conspiracy to murder a foreign official, after reaching a detailed plea bargaining agreement with the U.S. government. Townley is now serving 3 1/2 to 10 years in prison.

Three Chilean military men, including Contreras, have been indicted in connection with the killing, but the Chilean courts have refused to extradite them for prosecution. Two additional Cubans charged in the case are fugitives.