After repeated delays caused by the extreme delicacy with which the government views the case, court proceedings began today against a Salvadoran implicated in the assassination here last January of two U.S. agricultural advisers and the head of the country's land-reform program.

It has been nearly three weeks since the arrest of prominent businessman and playboy Ricardo Sol Meza. But it took until today for the government to take on the case. It is considered to be the first serious legal proceeding against a prominent Salvadoran rightist accused of political violence under the current government.

Fear of retaliatory attacks by political allies of those accused of thousands of political murders in the past 18 months have largely paralyzed the Salvadoran judiciary. Although a few leftist guerrillas have been brought to trial in that period, diplomats and judiciary officials here say they can remember no time when a member of the country's former ruling class, such as Sol Meza, has been put in the dock.

Indeed, many remember that after El Salvador's archbishop was assassinated while saying mass last year, the judge charged by the government with conducting an independent inquiry received so many threats to his life that he fled abroad.

So Meza is accused of being involved in the murders Jan. 3 of Michael Hammer, 42, of Potomac, Md., and Mark Pearlman, 26, of Seattle, both AFL-CIO advisers to El Salvador's controversial land reform program. The two Americans were slain in a hail of gunfire along with their host, Rodolfo Viera, the head of the land-reform program, as they sipped coffee in a restaurant in the Sheraton Hotel. Sol Meza has a financial interest in the hotel.

The Salvadoran's detention was extended pending decision by the judge whether to order his trial on charges of murder of being an accomplice. Sources close to the investigation here say that Sol Meza is one of a group of six well-known Salvadorans who were having coffee in a neighboring coffee shop prior to the assassination. Eyewitnesses place them after the shooting in and around the restaurant where the trio were killed.

A second suspect, Hans Christ, was arrested by the FBI two weeks ago in Miami. He apparently had fled there after Sol Meza was arrested by the FBI two weeks ago in Miami. He apparently had fled there after Sol Meza was arrested here April 5. The other four suspects, who were part of Sol Meza's group, are also believed to have fled abroad.

Sol Meza and Christ, who are both married to the daughters of one of El Salvador's most prominent landholding families, are suspected of having strong ties to extreme right-wing groups that have violently opposed measures like the land reform -- instituted by the military-civilian junta that overthrew the country's landholder-supported dictatorship in 1979.

Today's preliminary hearing was necessary under Salvadoran law to set the wheels of justice moving. The state prosecutor presented Judge Hector Enrique Jimenez, with a lengthy deposition of the state's case. When that had been typed up, the judge took depositions directly from Sol Meza and his lawyer.

Sol Meza was brought to the court from prison by a motley escort of non-uniformed police armed with submachine guns. He was hurried into court as he held a red bandanna over his face to thwart photographers who had been staking out the court for a week. Sol Meza made no comment before going into the closed hearing which lasted most of the day.

The case, court officials acknowledged in private, had been delayed until a judge courageous enough to take it on could be found and suitable security guarantees of protection were made by the government to all participants.

After several other judges begged off the case, Judge Jimenez, who has also been involved in the investigation into the assassinations of three U.S. nuns and a lay worker last December, finally agreed to take on the case yesterday.

The start of the legal proceedings here today will also set in motion Salvadoran extradition procedures against Christ in Miami.

Although the judge could still choose to drop the case on legal technicalities, U.S. officials here expressed confidence that this would not happen because of the government's embarrassment at the reactions in the United States as a result of the killings here of U.S. citizens which so far have gone unpunished.

Judge Jimenez, talking to journalists after the hearing, said the basis for charging Sol Meza was the testimony of a waitress at the hotel, Teresa Torres Lopez. The judge quoted her as saying in a deposition that she saw Sol Meza and Christ before the shooting and observed them signal two others who she said fired the shots. Torres, 41, is understood to be under police protection outside El Salvador.