San Salvador's influential Archbishop Arturo Rivera y Damas said today that the deaths of "30,000 or more people who have been murdered in this country outside of combat" have gone uninvestigated, while "curiously" soldiers have been arrested who allegedly killed U.S. citizens.

With customary cautious phrasing, Rivera y Damas focused his Sunday homily on abuses by the government military against its own citizens as the fundamental problem of justice in El Salvador. He spoke at a time when U.S. officials have called attention to the U.S. deaths and pointed to technical shortcomings as the source of apparent inadequacies of the Salvadoran legal system.

U.S. Attorney General William French Smith yesterday ended a two-day visit here designed to press administration and congressional demands for trials and convictions in the cases of eight murdered U.S. citizens, including four Catholic churchwomen, two agrarian reform advisers, a young tourist and a journalist.

In Smith's public statements he repeatedly raised the possibility that vitally needed U.S. aid would be cut by Congress if there are no convictions soon. "You could easily say in terms of our relations this is the most important issue," Smith said Thursday night.

He added, however, "It is not for us to impose on the Salvadorans what we think should be done."

Instead, the attorney general offered "U.S. expertise in dealing with due process." He suggested that improvements could be made through changes in judiciary pay scales, the establishment of an independent bar, revisions in the rules of evidence and "curbing intimidation" of judges and lawyers.

A six-person State Department "judicial assessment team" meanwhile is continuing a survey begun last week of the Salvadoran justice system to see where it might benefit most from U.S. advice, according to a spokesman for the U.S. Embassy.

Smith declined to comment on the specifics of any case "under adjudication."

Rivera y Damas, in his homily at the Metropolitan Cathedral, stressed the many cases that are not under adjudication and particularly stressed the abduction and murder of two people earlier this month in the Christian community of San Ramon near the capital.

The archbishop charged last week that members of the National Police, whose commander is a lawyer and a member of the government's human rights commission, did the killing. The police denied any connection with the murder.

Rivera y Damas noted that after "almost four years" 30,000 or more noncombatants have been killed. He added that "those murders continue, in many cases with victims pulled from their houses in the middle of the night."

"Curiously," the archbishop continued, "in the cases of North American citizens there are people detained who pertain to the security forces."

Five national guardsmen are accused in the 1980 murder of three Roman Catholic nuns and a lay churchworker. Three regular Army soldiers are under arrest for the 1982 killing of the tourist. Two guardsmen are detained in the case of the 1981 agrarian reform advisers.

Although military officers have been implicated in the advisers' case, the courts have released them. No arrests have been made in the 1980 killing of the journalist, whose body was only recently identified.

Smith said that "as of now there is nothing close to a conviction" in any of these cases.

Rivera y Damas noted, however, that "in the cases of the thousands of murdered Salvadorans very few have been brought to justice. Where are the perpetrators of those crimes? What wall holds back justice so that it almost never finds their authors? It's a question."

In the six days beginning April 8, according to Rivera y Damas, 114 people were killed in political violence, including 33 casualties acknowledged by the Army. The archbisbop advised his country's politicians today that they "had better look for the real causes of our evils so they can take adequate measures against them."

Rivera y Damas called "the common denominator" of the country's state institutions the "vacuum of power," but did not refer specifically to what is widely believed to be the imminent resignation under pressure of Salvadoran Defense Minister Jose Guillermo Garcia, the man who has dominated the armed forces for the last four years.

The archbishop particularly condemned what he called the "prevalence of personal interests over the common good."