Court investigations that for the first time formally implicate ranking officers in slayings and disappearances have deepened Argentina's conflict over abuses by its outgoing military government and raised fears of an officers' rebellion that could block scheduled national elections.

For more than a week, Buenos Aires' fine-grinding rumor mill has hummed with reports of a potential uprising by hard-line military officers determined to put an end to new judicial probes of disappearances and other human rights violations. Judges have already placed one former member of the ruling junta under detention and two former military presidents have been ordered into courtrooms for cross-examination.

Last week, as tension over the cases reached a high point, President Reynaldo Bignone, a retired general, admitted in a Cabinet meeting that his year-old administration, pledged a return to constitutional rule Jan. 30, had reached "it's most difficult moment." The Catholic Church, this country's state religion, condemned the "coup spirit" and "efforts to destroy the institutional process." Both Bignone and the church appeared to be attempting to avoid a move within the military to push back or cancel the timetable that calls for elections Oct. 30.

Bignone told the country in a television address that conflict over the military's past repression had become a serious obstacle to the democratic process. In an apparent effort to calm the spirits of a deeply divided military establishment, he declared that "in no way will a negation of the results of the war against subversion be permitted."

The maneuvering, while political parties moved toward selection of presidential candidates, reflected continuing indecision over how to resolve a traumatic period of political violence that triggered counterviolence by the military.

The issue, which now centers on the disappearance of approximately 6,000 to 15,000 Argentines at the hands of government security forces between 1976 and 1979, long has been viewed as the potential trigger of new round of the political anarchy that has plagued Argentina for two generations.

Despite frequent military attempts to decree an end to the controversy and attempts by political parties and the church to negotiate a solution, the conflict has continued to grow.

Gen. Fernando Verplaetsen, the chief of Buenos Aires provincial police and boss of three policemen now jailed as suspects in a recent disappearance case, declared they had "strictly followed orders" and suggested that the armed forces were prepared for a new campaign against "subversion."

"There is no possible discussion, nor armistice, nor forswearing of weapons, nor resignation, nor cease-fire," asserted Verplaetsen. The speech quickly touched off the coup rumors, and the tremors only increased when Verplaetsen's remarks were endorsed by the commander in chief of the Army, Gen. Cristino Nicolaides.

The response of some critics, who are seeking court trials for officers involved in disappearances and alleged corruption, added to the tension. Raul Alfonsin, a charismatic politician who appears to have clinched the presidential nomination of the second-largest party, the centrist Radicals, said Verplaetsen's ideas "carried the country back to 1976"--the year of the military coup--when "demons were fought with the weapons of demons, and so the inevitable occurred: Argentina became hell."

Conservative leader Pablo Gonzalez Bergez, a former ambassador to Canada, said, "Unless this man is put under arrest, the country's return to democracy will be a farce."

All three services have issued statements reaffirming their commitment to elections, and a meeting of top generals this week in Buenos Aires produced no visible move to postpone elections or remove Bignone, their strongest defender within the government.

Still, the political jitters continue, fed largely by the cautious but steady progress of two heavily publicized court investigations. One is by civilian courts of the shooting deaths two months ago of two leftists, while the other involves the 1977 disappearance of former ambassador to Venezuela Hector Hidalgo Sola.

Police said the slayings in May of two activists of the populist Peronist movement, Osvaldo Cambiaso and Eduardo Pereira came in a shootout with police along the Pan-American Highway outside of Buenos Aires.

Since then, Argentina's newly aggressive civilian court, prompted by human rights lawyers and press coverage, has punched holes in the official story. Witnesses have testified that the two men were abducted from a bar in the port of Rosario by heavily armed men in civilian clothes. Court- ordered tests have indicated that the Peronists were tortured before being shot at point-blank range.

"It is the first time that the human rights community has been able to unmask official explanations and rhetoric as lies in a courtroom," said Emilio Mignone, the head of the Center for Legal and Social Studies, a major human rights group. "All of this is creating military nervousness, and is causing them to seek reassurances from the politicians over their status in the coming democratic order," he added.

The military unease has been increased by the investigation into the disappearance of Hidalgo Sola. Last month, former military presidents Jorge R. Videla and Roberto Viola were cross-examined in court on their claims that they did not have the power to investigate the abduction.

In that case, as in the May slayings, traditional interservice rivalries and factionalism in the armed services have been key factors. Videla and Viola were Army commanders, but Hidalgo Sola is alleged to have been killed by the Navy. In the Peronist killings, police are reported to be angry because of what is said to have been the unacknowledged participation of the Army in the Rosario abductions.

Emilio Massera, the former Navy commander alleged to be responsible for the Hidalgo Sola case, has already been ordered detained in a third disappearance case. The retired admiral has been imprisoned since June 18 at a Navy base outside of Buenos Aires for suspected involvement in the 1977 abduction of a businessman.

Although Army leaders say they are united in a determination to block investigations of their involvement in the repression, many political leaders believe they are quietly backing court efforts to investigate Massera. The civilian judge in the case, Oscar Salvi, has grown so confident that he recently was quoted as predicting that Massera could be in jail "for a long time."