The U.S. government has officially asked the Chilean government to produce for questioning two members of its military -- who also are believed to be Chilean secret police agents --who have been linked by American investigators to the car-bombing murder of former Chilean ambassador Orlando Letelier here.

Yesterday's extraordinary public disclosure of the request was seen by diplomatic and legal sources as an indication that the federal government has reached the point in its sensitive, and so far highly secret, investigation that it wants to bring public pressure to bear again the Chilean government to force it to cooperate.

"This is obviously a situation where other diplomatic and investigative channels were thoroughly utilized before taking this route of public disclosure," one person familiar with the 17-month-old investigation said. "We want these men produced and these questions answered and we are aware of the possible diplomatic ramifications."

According to the documents filed yesterday, the two men entered the U.S. a month before the murders of Letelier and an aide at the Institute for Policy Studies, Ronni Moffitt, who were killed when a bomb blew up their car as they drove to work in September 1976. Both died minutes after the 9:35 a.m. explosion on Sheridan Circle NW.

"At least one of these men met with one of the persons believed to be responsible for these murders," according to the official "request for international judicial assistance" document filed yesterday in court. Diplomatic and legal sources said the delicately worded "request" could be read as a clear indication that the investigators believe persons high in the Chilean government had advance knowledge of the Letelier assassination plan.

The document did not identify the persons believed to actually have carried out the bombing, but informed sources previously have identified those persons as anti-Castro Cubans who were acting under the direction of DINA, the Chilean secret police.

Although previously published reports have indicated that DINA agents were the prime suspects behind the bombing, yesterday's document was the first public acknowledgement that the investigation had focused on members of the Chilean government. The two men were identified in the documents solely as "members of the chilean military," but investigators said they were believed actually to be DINA members.

Specifically, the American government is requesting that a Chilean court question the two military men there in the presence of an American prosecutor, Eugene M. Propper of the major crimes division of the U.S. attorney's office who has been coordinating the investigation. "It is believed that these men have knowledge and information concerning these murders," the document said, and it requested that Propper participate in the questioning.

According to the court record, the two Chilean military men obtained visas to enter the U.S. early in the summer of 1976 by using fraudulent documentation from a country other than Chile. When the U.S. found out the documents were fake, the visas were revoked on Aug. 9, 1976, the document said.

The same two men returned to the U.S. Embassy in Santiago, Chile, on Aug. 17 with official Chilean passports and were issued multiple entry visas into the U.S. for a six-month period on the basis of that official identification according to the document filed in court.

The two men were identified as Juan Williams Rose, 28, of Santiago, and Alejandro Romeral Jara, 26, also of Santiago. Their photographs were provided to the Chilean government, but other copies were kept under seal in court records here.

The document filed yesterday signed by U.S. District Chief Judge William B. Bryant, asked that the interrogation be conducted "as expeditiously as possible."

Deputy Secretary of State Warren Christopher personally handed the document -- legally known as "letters rogatory" -- to the Chilean ambassador last Friday, the State Department and the Chilean Embassy confirmed yesterday.

Amenabar Tomas, minister-counselor of the embassy, said the document has been sent to Chile and would be handled through the normal legal channels. "The Chilean government has offered its full cooperation," Tomas said.

A State Department official said "it is very difficult for us to comment on something that is still under active investigation." He said, therefore, that there was nothing he could say about the possible diplomatic impact of the public disclosure of possible Chilean involvement in the assassination.

Letelier, 44, had been ambassador to the United States and a cabinet minister in the Marxist government of the late Chilean President Salvador Allende. Moffitt, 25, had been a staff member of the Institute for Policy Studies here, where Letelier worked.

The murders have provoked a painstaking and massive federal investigation into the shadowy network of Latin American conflict, including the alleged terrorist activities of anti-Castro Cubans in the U.S.

The Justice Department and the FBI, under prosecutor Propper's direction, have questioned persons around the world in connection with the murders.

The investigation -- along with some help from the CIA in foreign countries -- has relied heavily on FBI informants in Cuban communities in the United States, sources have said.

Through those informants, the investigators believe they have been able to piece together a scenario in which Chilean military officials flew into the U.S. and met with willing Cuban terrorists who agreed to assassinate Letelier, who had become an outspoken critic of the current Chilean military regime headed by Gen. Augusto Pinochet.

The informants who talk furtively to FBI control agents in Cuban communities in Miami, New York City and elsewhere refuse, however, to appear before a grand jury or publicly testify because they are afraid of violent retaliation, sources said.

One Cuban movement leader, Jose Dionisio suarez, has already been jailed for 10 months for refusing to testify before the grand jury after being granted immunity. Other Cubans have made it clear to investigators that they would also go to jail before testifying, sources added.

At one point during the investigation, the probers used the same "letters rogatory" route disclosed yesterday to question Orlando Bosch, head of an anti-Castro umbrella group, in connection with the Letelier investigation. Bosch is in jail in Venezuela in connection with the bombing of a Cuban airliner in which 73 persons died, and reportedly was of no assistance to the Letelier probers in that secret interrogation process.

Guillermo Novo, another member of a Cuban group in New Jersey has been a fugitive since last June after he failed to appear at a Trenton, N.Y., hearing on whether his parole on a 1974 explosives conviction should be revoked.Investigators in the Letelier case had asked for that revocation after he refused to cooperate with them.

When he was in Washington last September to sign the Panama Canal treaties, Gen. Pinochet was questioned by reporters about stories printed at the time concerning DINA's alleged involvement in the Letelier assassination.

"I can swear that no one in the Chilean government planned anything like that," Pinochet replied. "Letelier was detained in Chile, and I was the one who gave him his freedom and authorization to leave the country freely."