Michael V. Townley, the confessed assassin in the 1976 bombing death here of former Chilean ambassador Orlando Letelier, testified yesterday that he has no regrets about committing the murder.

Townley, an American-born agent for the Chilean secret police and the government's key witness against three anti-Castro Cuban exiles charged in connection with the Letelier killing, told a federal court jury that Letelier was an enemy of the chilean government.

"He was a soldier and I was a soldier," the 36-year-old Townley said matter-of-factly. "Within his own party, within his own actions, he was carrying on a battle against the government of Chile.

"I am not saying that I agreed with killing him, either," Townley said. "I received an order and I carried out the order to the best of my ability." Townley has earlier testified that his instructions came from an official of the Chilean secret police, once known as DINA.

But Townley, who has said he personally planted the bomb underneath Letelier's car, added yesterday that he "very much" regrets that Ronni K. Moffitt also was killed in the explosion. She was a colleague of Letelier's at the Institute for Policy Studies and a passenger in his car when it blew up on Washington's Embassy Row the morning of Sept. 21, 1976. Her husband, Michael, was injured in the explosion.

Townley's testimony came in answer to cross-examination questions put to him by Paul Goldberger, one of three defense attorneys representing the Cubans on trial, Guillermo Novo Sampol; his brother, Ignacio Novo Sampol, and Alvin Ross Diaz. Guillermo Novo and Ross are accused of the two killings, while Ignacio Novo is charged with lying to a grand jury investigating the slayings.

While not specifically questioning Townley about his testimony implicating the three defendants, Goldberger elicited several statements from him that could hurt the prosecution's case.

Townley testified that he plotted with two Chileans indicted in the case -- former DINA director Juan Manuel Contreras Sepulveda and DINA agent Armando Fernandez Larios -- at Nicco's Pizza Restaurant in Santiago last February to decide how they would respond to a Chilean investigation into the Letelier case.

"A line of action was decided," Townley testified, conceding that it amounted to telling lies and halftruths to Gen. Hector Orozco Sepulveda, the Chilean chief of military intelligence and the man assigned to investigate the Chilean involvement in the Letelier assassination.

Townley gave the statement to Orozco last March 29. Contreras' lawyer supplied it to Goldberger only this past weekend, and the availability of the statement surprised prosecutors who had had been seeking it for months.

Townley said he gave several incomplete statements to Orozco in which he totally omitted mention of a 1975 mission he undertook to Mexico to "eliminate" two Chilean exiles. The two, like Letelier, were highly critical of the current Chilean military dictatorship of Augusto Pinochet.

The tall, husky Townley said he considers Chile his homeland and hopes to return there after completing his sentence.

Townley testified that he had told U.S. investigators nothing about his role in the Letelier killing until he had a firm, signed deal with the U.S. government -- a 3 1/2-to-10-year prison term, with a government recommendation of parole after 40 months, in exchange for a guilty plea to a charge of conspiring to murder a foreign official.

U.S. District Court Judge Barrington D. Parker ruled yesterday, however, that Townley can invoke the Fifth Amendment if he feels his answers will tend to incriminate him in Chile. The judge said Townley's "fear of incriminating himself by answering is real and substantial" because of a Chilean law prohibiting disclosure of state secrets.

Townley nonetheless testified that he received so-called "electric matches," one of which was used in the Letelier bombings, from a DINA agent named Ernesto "in charge of the section of disarming or handling explosive devices." Townley had refused to divulge that information on Friday.