...while regime itself grows more belligerent to US pressure

Despite deepening concern over the repressive tactics of Chilean Gen. Augusto Pinochet Ugarte, Washington doubts that it can exert much influence on him and his 11-year-old government.

The Reagan administration is stepping up verbal pressure on the Pinochet government, but there is a sense of frustration that the United States does not have much leverage with the Chilean strong man.

The frustration is heightened by the realization that as far as General Pinochet and his colleagues are concerned, the US is largely irrelevant, ''a nuisance that he has to live with,'' as a leading Chilean dissident here put it.

In recent weeks, the US has departed from its more traditional ''quiet'' diplomatic style to publicly criticize the South American country - particularly for what is perceived as General Pinochet's turn from earlier promises of a transition toward democracy.

The current state of emergency in Chile, imposed early last month by General Pinochet amid new demonstrations against his government, was extended Dec. 17 for another 90 days. The emergency allows the government to restrict press freedom, ban meetings, and send citizens into domestic or external exile. The Pinochet government has used the powers extensively, sending several hundred opponents to exile in northern Chile.

''What to do about Chile,'' says one US source, ''has been a top issue for analysis in Washington'' recently.

The State Department, the White House, and the Pentagon all have been involved in this analysis. While there is general agreement that US policy options on Chile are limited, there is also accord that the US should ''make abundantly clear where it stands'' on Chile.

As a result, US officials are stepping up contacts with Chilean officials and with opposition groups.

Many opponents of the Pinochet regime are calling on Washington ''to do something for us,'' as a leading member of Chile's important Christian Democratic Party said here in an interview. But Washington is hard put to come up with specific help.

Although Chile is taking on more of a pariah image in Latin America - it is one of the few holdouts of military government as much of the region moves toward democracy - its somewhat isolated geographic position insulates it from the democratic trend elsewhere. The strong support Pinochet still enjoys in several sectors of the Chilean population contributes to this status as well.

''It almost seems that the tall Andes Mountains on our east and the deep Pacific Ocean on our west make us immune from the democratic currents elsewhere, '' says a prominent Chilean Socialist who is in the US trying quietly to drum up Reagan administration support for ''some sort of action against Pinochet.''

Like many Chileans, he is frustrated that the opposition to General Pinochet has not been able to coalesce effectively to form a united front against the dictatorship. He evades placing blame on anyone or any group.

''We just don't seem to be able to agree on how best to deal with Pinochet,'' he says. ''That's why I am here trying to see if there are things the US can do to help.

''It is a bit strange that I'm here. After all, I reject the US role in bringing down the Allende government. But despite that role, I think the US would like to see something in Chile other than Pinochet and so I am hoping that somehow we can work something out.''

A US source says: ''It is a plaintive cry for help, an admission that they cannot do it (get rid of Pinochet) themselves.''

Still, there are some Chile specialists in the administration who say that eventually the more moderate Socialists, along with the centrist Christian Democrats and the moderate rightists, should be able with the help, perhaps, of Chile's Roman Catholic Church to work out a democratic alternative to General Pinochet.

This is one of the messages Washington is trying to get across to the Chilean opposition. At the same time it is telling Pinochet and his supporters that it looks with disfavor on his delay in carrying out his promises to move toward a democratic transition.

After 1983 public protests, the Chilean government began holding talks with some opposition leaders, but in August Pinochet make a point of publicly announcing that Chile was ''not yet ready'' for democracy. The general plans to stay in office until at least 1989.

Military government is a departure from the nation's long democratic tradition. For decades until 1973, Chile had been regarded as a bastion of democracy in Latin America. Its military stayed in the barracks. But a brutal military coup in 1973 that overthrew the Marxist government of Salvador Allende Gossens and brought General Pinochet to power snuffed out that tradition.

In earlier years, particularly in the 1960s, the Chilean-US relationship was warm and cordial. The friendship slipped considerably in the Allende years as the US sought to destabilize his government. Friendly ties were not renewed under Pinochet, although Washington was relieved that the Marxist inclination of the Allende years had ended.

When Jimmy Carter was US president, the US government strongly criticized Chile for human-rights abuses. The Reagan administration toned down the attack and tried, instead, to work through diplomatic channels to affect change in Chile. But the current shift in US policy suggests to some observers an acknowledgement that the soft approach as failed to nudge Chile closer to democracy.