The accord among Chile's political opposition this August to press for a return to democracy is becoming a watershed event in the country's politics, but so far it has failed to bring about the desired goal.

The accord, signed on Aug. 25 by most opposition leaders, outlined a set of democratic principles and general steps for a return to civilian rule after 12 years of military dictatorship under Gen. Augusto Pinochet. Since then, political discussions have treated it as a kind of historical pivot, dating events in terms of whether they happened before August or after.

The accord initially gave the opposition new momentum in its drive to break the political stalemate with the Pinochet government, but recently that momentum has dwindled. Pinochet, initially caught by surprise, has recovered and gone on the offensive, according to politicians, diplomats, journalists and other analysts here.

On the surface, Chilean politics look like a game of King of the Mountain, in which challengers clamber up a hill attempting to dislodge a reigning figure. But the struggle in Chile has a complexity more like chess than a children's playground sport.

With the opposition splintered into more than a dozen parties, reflecting a wide range of ideologies from Communist to nationalist, agreement has been rare.

The August accord, signed by representatives of 11 right-wing, centrist and left-wing parties and mediated by Cardinal Juan Francisco Fresno, was the first multiparty agreement on moves to end military rule. But almost from the moment the document was publicized, its promoters fell into squabbling over just what it represented.

For rightist parties, whose split from Pinochet was a serious loss for the Army general, the accord was to be a starting point for negotiations with the government about a peaceful transfer of power.

But for the left, which has opposed talks, figuring Pinochet is still too strong and will weaken in time under pressure to leave office, the accord was seen simply as a grand statement of principles and concepts.

Differences in bargaining strategy among the parties were skirted in the accord, which was purposefully vague about the timing of its demands for full restoration of freedom, legalization of political parties, establishment of electoral registers and the holding of a plebiscite. Unity was found in a common call for direct presidential and congressional elections and in support of a mixed economy and the right to private property.

Pinochet's rejection of the accord -- he ridiculed its drafters as "pseudopoliticians" and said the document lacked clarity -- forced opponents to consider what to do next.

Last week, the accord's three-man coordinating team formally requested a meeting with Interior Minister Ricardo Garcia. The minister accepted but offered no date for the meeting, which would be the first between the two sides since publication of the accord.

"We don't expect the government to offer anything," said Gabriel Valdes, leader of the centrist Christian Democratic party. "But part of our strategy is to expose the government nationally and internationally as the side that doesn't want to change anything."

Chile's government spokesman and its interior minister declined several requests for interviews.

In the past month the government has made clearer its intention to carry on past 1989. That is the year, according to the 1980 Constitution written for Pinochet, in which Chileans are to be asked to vote on a single presidential candidate to be nominated by the four-man military junta.

Pinochet, 70, has hinted he could be the candidate. In any case, he has suggested his country will still need military rule then to battle the Communists, whose influence has been rising, particularly among students and intellectuals.

It is the democratic opposition's conviction that Pinochet intends to retain power for life. But some still hope other military commanders may be persuaded by public sentiment against Pinochet, and by the ability of opposition groups to show they can act responsibly, to oust the Army general and oversee a rebirth of civilian government.

One of the most significant results of the accord has been the highlighting of differences within Chile's military over the political future. A number of opposition politicians and foreign diplomats said they suspect that the Air Force and Navy commanders and possibly the national police chief -- all junta members -- are challenging Pinochet on staying in power past 1989.

"For the first time, cleavages in the military have become evident since the accord," said Andres Allamand, leader of the rightist National Union party.

Air Force commander Gen. Fernando Matthei earlier this month expressed sympathy for the accord, saying that if it did not exist, the government would have had to create it. He said the government "had committed large mistakes" by refusing to talk to critics, and it was time to "open the doors of dialogue."

A further hint that Pinochet may be facing increased resistance from inside the military was the early and presumably forced retirement in November of general Cesar Benavides, the Army representative on the junta. No reason was given for the move, which was interpreted as a slap at Benavides for taking a pro-accord attitude.

Another factor pressuring Pinochet has been a shift in U.S. tactics. The Reagan administration is not yet outrightly opposing the Chilean dictator, but it has spoken approvingly of the opposition accord and is trying to encourage Pinochet and his critics to reach a consensus.

The U.S. administration initially pursued a policy of "quiet diplomacy," cultivating relations with Pinochet while nudging him toward accommodation with Chile's moderate opposition. U.S. officials are anxious to guard against Chile becoming a South American version of Nicaragua. A Marxist coalition elected in 1970 ruled until the 1973 coup.

But Pinochet abandoned dialogue and began a campaign of repression against widespread strikes and leftist violence that broke out in 1983 and 1984. This prompted a reassessment of U.S. policy.

The resulting change in American posture has been sharply demonstrated by Harry Barnes, the new ambassador. Since arriving in November, Barnes, a career diplomat who served as director general of the Foreign Service during the Carter administration and came to Chile from an ambassadorship in India, has upset Pinochet by speaking bluntly about the need for more democracy in Chile.

Barnes has been quick to contact opposition leaders and human rights activists, visiting them even before meeting with all the junta members.