After a week of unprecedented antigovernment protest, Gen. Augusto Pinochet appears to be in danger of losing control of a country long mired in economic crisis and increasingly dissatisfied with his decade-old military rule.

Huge demonstrations in Chilean cities and a major strike by copper workers have changed the opposition from an assortment of scattered, easily controlled activities to a powerful movement whose agenda has shifted from economic themes to open calls for a return to democracy.

Today, copper workers in the El Salvador mines said they were continuing their strike for a third day, while unions at two other mining centers that carried out a 24-hour strike Friday, El Teniente and La Andina, said they were considering renewing their action for an indefinite term.

The powerful copper union is the backbone of an opposition movement that has called two national days of protest against Pinochet in the last two months.

The result has been a political challenge unthinkable only months ago in a tightly controlled society, and an evident wavering by Pinochet's authoritarian government.

Pinochet, who only two years ago triumphantly put into effect a new constitution mandating his rule until at least 1989, has appeared isolated and indecisive so far in responding to the growing crisis.

"He seems not to understand what is going on in the country," said a conservative leader who still supports military rule. "He seems to have completely lost his capacity for leadership."

Most politicians and diplomatic analysts here believe that Pinochet will not be quickly or easily dislodged from what they describe as a powerful base in the armed forces. But they say the 67-year-old leader will have to take strong measures of either repression or liberalization to reverse his decline--and that the government has appeared unwilling or incapable until now of carrying out such action.

Pinochet repeatedly threatened a harsh crackdown this week on both a newly formed opposition labor coalition and Chile's officially proscribed politicians. But after meeting through the day with top government and military officials, he announced only vague measures in a television address last night.

Government authorities today announced the firing of 1,800 copper workers participating in strikes, legal action against their leaders, and the military takeover of the mining centers of El Salvador and Chuquicamata, the largest Chilean mine that has delayed a strike action. Two leaders of opposition construction and farm workers unions were also reported arrested.

Some analysts and politicians believe, however, that Pinochet has encountered strong opposition inside his government to fully applying "the strong hand" he promised against politicians. By today, no action had been taken against political party figures and the government had backed off from an apparent earlier intention to summarily expel union protest leaders from the country.

At the same time, Pinochet has taken only tentative steps toward liberalizing his government and shoring up waning support among conservative political sectors and business groups that once formed a key base of government legitimacy.

Since the first national day of protest in May, Pinochet has sought to stimulate Chile's economy out of a deep recession, ease the debt burden on businessmen and mobilize supporters in a "civilian-military movement." Last night, he also responded to two demands of conservative civilian supporters by promising to permit the return of some Chilean exiles and ending censorship in book publishing.

Most conservative leaders have not supported the new labor-based national protest only because they see "no civilian alternative to Pinochet," said the conservative leader, who asked not to be named. "But our attitude is very confused," he added. "No one is sure what to do."

The political uncertainty extends to opposition political parties and even the militant labor movement, which has been surprised by its success in organizing the demonstrations and subsequent strikes this week. While copper union leaders have sought to draw other key unions into an indefinite national strike, several unions--including one of copper's own divisions at Chuquicamata--have so far appeared reluctant to commit themselves to a full-scale confrontation with the government.

Despite the successful organization of an opposition labor coalition in the National Command of Workers for the Protest, the Chilean opposition remains relatively disorganized by years of government repression and deep political divisions dating from the 1973 downfall of the socialist government of Salvador Allende.

Some labor leaders complain that political parties, traditional vehicles of mobilization in Chile's highly politicized society, have lagged behind in opposing the government. "The parties don't want to get involved in anything," said a leader of the petroleum workers union and National Command. "They only want to wait and prepare for whatever will come afterward."

Many political leaders, in turn, concede that they are not yet in a position to offer a cohesive alternative to military rule and warn that the copper union may have given the government the opportunity to damage the labor union with mass firings following the launching of the illegal strike.

These opposition weaknesses, politicians and other analysts add, remain a key factor in Pinochet's ability to maintain his position within the Chilean armed forces, the institution that will utimately determine any change in government.