The door to civilian rule in Chile has opened a crack - and suddenly there is an unrelenting clamor for the door to swing wide open. ''We are in this to put an end to military rule,'' says Gabriel Valdes Subercaseaux, head of the new Alianza Democratica, an amalgam of six political parties that have joined forces in opposition to the military government.
Chilean leader Augusto Pinochet Ugarte clearly has no intention of giving up power. But as the 10-year anniversary of military rule approached last month, Pinochet, under pressure, agreed to give civilians a modicum of influence in government.
He named a new, largely civilian Cabinet and held out the prospect of a national plebiscite on the issue of holding congressional elections before the scheduled date of 1990. Beyond this, he eased censorship, promised to legalize political parties by next year, and allowed some 3,000 civilians to return from exile.
These concessions do not satisfy Alianza, however. Flushed with their recent gains and the upsurge of political debate here, they are not giving up on a speedier return to civilian rule.
''It is not enough,'' Mr. Valdes says, ''for the government to suggest holding a plebiscite to amend the Constitution to hold congressional elections before 1990 as scheduled. There has to be more.''
Alianza wants Pinochet to step down before 1989, the date set for his term to end under the nation's new constitution. The group is not calling for his immediate resignation, however. It knows that is too much to ask.
At the moment, Alianza is the key force of political opposition. Its leadership is largely centrist and is dominated by the Christian Democrats, Chile's largest political party. The group does not include the far right or the far left.
Christian Democratic influence in Alianza may slip a bit in October as Hugo Zepeda of the Republican Right assumes the Alianza presidency for a month. Mr. Zepeda tends to be closer to the Pinochet government than other members of the Alianza. But the emphasis on a legitimate dialogue with the government - and the broad Alianza tone set by the Christian Democrats - will continue.
Other political groups, including two on the left, are forming, too. But there is no current plan for them to be included in any dialogue with the government.
Nevertheless, after 10 years in limbo, politicians are speaking out forcefully. They are no longer circumspect in their criticism of the military government, although they do hold back from criticizing General Pinochet directly.
Andres Zaldivar Larrain, a former Chilean senator and a Christian Democrat like Mr. Valdes, says Pinochet's rule has been ''the worst government in the history of Chile.''
A couple of years ago such statements would have promptly sent Zaldivar to jail or to exile. Indeed, he was sent packing in 1980 after a Mexican newspaper inaccurately reported his comments on the military government.
Now it seems that virtually anything can be printed - right here in Chile. Newspapers and magazines are full of criticism of the government.
It is a spectacular change after years of military censorship.
But there are warnings that the freedom is relative, that it might not last. ''The hand that giveth can also take away,'' says a military leader close to Pinochet. He adds enigmatically: ''Beware.''
Such warnings do not deter the politicians - or the hundreds of thousands of Chileans living in the poblacionesm, the shantytowns that ring this capital city. The poor are increasingly restive. A frustrated, largely jobless, and angry people, the pobladores have been willing in the past several months to risk violent confrontations with the carabinerosm, Chile's national police, to protest the nation's political and economic policies.
Chile is in the throes of an economic recession as bad as the depression years of the 1930s. Economy Minister Carlos Francisco Caceres admits the rate of unemployment is more than 17 percent. Many Chilean economists say it is more like 30 percent.
Beyond this, there is a growing national feeling - perhaps not yet a consensus - that 10 years of military rule is more than enough. Ten years seems a long time - particularly when that rule has been heavy-handed and ''basically un-Chilean in its approach,'' says a prominent socialist, who asks that his name not be used.
Alianza and the confrontations between the pobladoresm and the police are only two points of antimilitary sentiment. And the military is becoming worried.
Some officers worry that the military could be irreparably harmed if more compromises are not made to assuage civilian wrath.
It is widely believed here that the recent overtures to civilians are a direct result of military men prodding General Pinochet to make them. In addition to naming a largely civilian Cabinet and opening a dialogue between the government and the opposition politicians, the government has:
* Allowed the return to Chile of more than 3,000 exiled politicians and others, including Christian Democrat Zaldivar. Those returning range from those on the moderate right to the moderate left. Still proscribed are hundreds of leftists - socialists, Communists, and others.
* Lifted the state of emergency that has been in effect since 1973, when the military seized power. The step ends the nighttime curfew and the arbitrary detention of suspects at secret government hideaways.
* Reinstated the rights of citizens to hold public meetings and protests without prior authorization - as long as these activities take place ''without arms.''
* Removed most limits on freedom of the press. Newspapers and magazines are freer to comment on the affairs of government, and some other publications are about to reappear - such as Politica y Espiritum, a Christian Democrat publication.
But there is still some censorship. The television interview program ''Encuentro'' was canceled by the government last week when Christian Democratic leader Zaldivar was to appear.
Without fully explaining the action, Alfonso Marquez de la Plata, secretary-general of government, said the government held the program ''not appropriate for the present moment'' and that it was ''suggested'' to the rector of the University of Chile, which runs the channel on which the program was to appear, that he cancel it.
Raquel Correa, host of the popular show, protested. She said: ''I am pained, angry, and frustrated'' by the action, adding that she does not now believe ''a political opening'' exists.
She is not alone. Despite the various decrees that end particular aspects of military rule, many Chileans feel they are little more than window dressing to keep the military in power.
Moreover, there is some feeling that these steps would not have been taken if recent antigovernment demonstrations had not brought serious concern to the military.
While that point has some validity, Chile's much-touted political liberalization actually began before the worst of the clashes between antigovernment demonstrators and the police in mid-August. At least 27 people were killed and more than 100 wounded, with a thousand or so detained in that clash. The military used brute force to crush the protest, sending 18,000 Army troops into the streets of Santiago against the unarmed civilians.
Immediately after that incident, General Pinochet declared the country was stable enough to lift the stage of emergency and asked the Roman Catholic Church , with which he has long feuded, to arrange a meeting between the newly named interior minister, Sergio Onofre Jarpa Reyes, and opposition politicians of the Alianza.
Several sessions have taken place. But the dialogue has been broken off by the opposition because of subsequent heavy-handed police attacks on some of the opposition leaders and the arrest of Rodolfo Seguel Medina, leader of the copper workers' union.
''How can you dialogue with someone,'' asks Mr. Valdes, ''who talks one minute and hoses you down the next?'' - a reference to police using water hoses on him and other political leaders during a demonstration Sept. 9. Large demonstrations took place last week, as well.
Where the liberalizations go from here is an open question.
At the moment, Interior Minister Jarpa says the government fully intends to support the political liberalization. But he does not give many details.
Mr. Seguel has now been released and charges against him dropped. But it took his 11-day hunger strike, the protests of the Alianza, and the intervention of Juan Francisco Fresno, the new Roman Catholic archbishop of Santiago, to secure his release. General Pinochet said he released the labor leader as ''a special deference'' to the archbishop.
Opposition leaders are clearly wary.
Alianza leader Valdes says, ''There will be dialogue only to produce change and not to strengthen the regime.''
How to assure that is probably the biggest challenge facing the opposition.