The bomb went off at 7:30 last night on the front steps of the Labor Ministry. This morning workmen were cleaning away the shards of glass and bits of human flesh from the front of the demolished building.

Employes of the ministry stood around talking of the six dead and especially of the woman they knew who sold coffee and snacks in front of the building. Her head was blown into the next block and her leg was still missing.

"We guess it was the subversives who did it," said one woman who worked in the building. "But we never know."

The outright war that began in January with a failed guerrilla offensive has cooled because the Salvadorean people refuse to support a general uprising. But the terror continues.

The terror has been fostered by all sides of the conflict here -- the guerrillas, the extreme right and elements of the government. The tactic was to bring the Salvadoran people to the point where they would say, en masse, basta ya, enough already, and give their support to whoever promised to end the violence. They have rejected the left, but thus far have embraced no other savior.

The Reagan administration may have made the commitment for them, however. The most radical change in Washington policy under the new administration -- at least inside El Salvador -- has been to focus on the guerrillas as the primary, virtually the only, source of terrorism in the country.

This shift in emphasis, more than increases in military aid or denunciation of Cuban and other communist arms shipments to the guerrillas, is already affecting the delicate balance of forces between moderates and conservatives in the government here.

There are strong indications it may end in the use of tactics and the implementation of policies discarded as too ruthless and repressive by the Carter administration.

It is too early to say for certain. Authoritative Western sources here are suggesting that to end the terrorism, the United States may look favorably on strategies followed in military-led nations such as Uruguay, where dissent was effectively quashed as subversives were eliminated.

More conservative elements here have long advocated the roundup and imprisonment or execution of all suspected leftist subversives, much like that carried out by the Chilean dictatorship of Gen. Augusto Pinochet.

That is not exactly what the Reagan administration appears to be contemplating, according to these sources. A general clean-up would be coupled with movement toward the election of a constituent assembly in order to provide a democratic opening or at least a democratic facade for the current, self-appointed, U.S.-backed government.

The possibility of a negotiated settlement between the government and the left, meanwhile, is disappearing rapidly. An opening for discussions in West Germany earlier this week was rejected by both the newly reinforced government here and the increasingly defensive, intransigent leaders of the revolutionary left.

Conservative Salvadoran businessmen who clearly have the sympathy and support of the Reagan administration are saying that negotiations are not necessary or desirable. The left should not be given anything.

A striking contrast between the Carter and Reagan policy here was apparent this week when the acting U.S. ambassador, Frederic Chapin, told the American Chamber of Commerce in El Salvador that he felt "right at home" with them. A year ago, then-U.S. ambassador Robert White all but accused these same people of funding right-wing death squads at a similar luncheon.

The Carter administration, and especially White, believed that the most dangerous threat to the stability of a moderate government in El Salvador came from the extreme right, including members of the government's armed forces.

But first as the guerrillas launched their offensive in January and then as the Reagan administration emphasized the outside threat to the Salvadoran government, changes sought by moderates in the structure of the Salvadoran armed forces have been postponed perhaps indefinitely.

Several top commanders, including the chief of the treasury police, whose troops are among those suspected of involvement in the December killing of four American churchwomen, were supposed to be removed from their posts in early February, according to a secret understanding between the Christian Democrats in the government and the armed forces high command, informed sources said.

Those officers are still in place.

One argument used by Washington for increased involvement in the supply and training of Salvadoran troops is to help bring them under better control and reduce the number of what the State Department calls "abuses," meaning murders and acts of torture.

But of the estimated 15,000 uniformed government troops, 7,000 are members of the security forces, which, technically at least, are police. United States law specifically prohibits Washington from training or supplying foreign police forces. The legislation dates back to scandals a decade ago involving U.S. personnel who were training Uruguayan and other police forces to interrogate and torture.

Now in El Salvador the United States cannot train police forces to torture, but neither can it train them not to.

The embassy here under the Reagan administration has considerably reduced its profile across the board, and its public demands on the ruling junta also have faded away.

Western sources question whether the embassy has any intent or desire to intervene, as it did frequently under the Carter administration, in the delicate relationship between the civilians and the military in the current government.

The civilians were put there in the first place as a result of strong insistence from the United States, and the Christian Democratic Party was maintained there for the last year with the help of fierce arm-twisting from the Carter embassy to ward off the extreme right.

Although the new administration in Washington reiterates its support for the current moderate government and says it wants to see it continue, Western sources here say the Reagan administration is not defining specifically what it considers "moderate" to mean.

None of this is to say, however, that some sort of economic reforms are not considered necessary in this tiny, densely populated country. After nearly a year of waiting, the phase of the agrarian reform giving sharecroppers title to the land they work was implemented earlier this month and thus far 800 titles have been distributed.

The most conservative elements of Salvadoran society have not been given carte blanche by the United States to drag the country back in time. But few desire to do so any longer.

Even the most conservative Salvadorans have begun to recognize the political efficacy of the agrarian reform in taking support away from the guerrillas. Until the implementation of the reform's second stage collectivizing farms larger than 290 acres -- most of the rich coffee farms in the country -- no overwhelming change will take place in the current economic foundations of El Salvador. That stage has been indefinitely postponed and the U.S. Embassy, even under White, was beginning to suggest that it should never be begun.

The message being received by conservative Salvadorans is that if the guerrillas and the terrorists, especially leftists, have to be eliminated altogether to achieve peace, then so be it.

That is what the conservative military and the small middle class here had hoped to hear all along.

"If Carter had won in the United States," said one businessman this morning, "we would be in the hands of the communists now. Reagan is our savior."