As Laurent Kabila's rebel juggernaut rolled across Zaire for the past seven months, U.S. officials scrambled repeatedly to devise a response that would contain the conflict without perpetuating the corrupt rule of President Mobutu Sese Seko.

But events outran diplomacy, partly because Washington had multiple and sometimes competing objectives. Zaire's neighbors rebuffed U.S. entreaties to stay out of the conflict, and now one of Africa's biggest and potentially richest countries has fallen under the control of a leader over whom the United States apparently wields little influence.

Kabila's triumph has many positive effects, Clinton administration officials said. It gets rid of Mobutu, whom the United States supported during the Cold War but who no longer had value as a strategic proxy. It should stabilize the fragile peace in neighboring Angola by cutting off Zairean support to longtime rebel leader Jonas Savimbi, another former U.S. protege who outlived his usefulness. And it reinforces Zaire's eastern neighbors, especially Uganda, which Washington supports in its conflict with Sudan.

Still to be answered, however, is the question of what kind of regime Kabila plans to establish in Kinshasa. The United States is pressing for multiparty elections and has promised Kabila financial and logistical support to conduct the balloting and effect an orderly transition to democratic rule, administration officials said. But there is deep concern in the administration that Kabila will eventually be not much different from his predecessor.

"We don't want the replacement of one autocratic regime by another, though that might be what we get," one senior official said. Eradicate Mobutuism'

According to Rep. Cynthia McKinney (D-Ga.), who met with him last week, Kabila "is committed to having free and fair elections that include participation by all political parties, and he expects that there will be many parties because that's the nature of Zairean politics. His first objective is the eradication of Mobutuism, and then the rebel alliance would participate in the elections."

Others who have observed Kabila, however, have said he tells people what he thinks they want to hear and that he has shown signs -- especially in his treatment of Rwandan Hutu refugees his troops encountered on their drive across Zaire -- of brutality and a thirst for revenge. In their view, the stage described by McKinney as "eradication of Mobutuism" might last years.

According to senior U.S. officials, as Kabila's rebellion arose and spread, Washington was repeatedly caught by surprise -- first by the insurgency itself, then by the speed of its advance, then by the eagerness of Zaire's neighbors to help put the skids to Mobutu. Priorities kept shifting in response to events on the ground, officials said, but there was one constant element: The United States would do nothing to perpetuate Mobutu's regime.

Even in pressing for a cease-fire last winter, officials said, the United States did so on the understanding it would be a prelude to transition, not a pretext for leaving Mobutu in power.

Three times during the Cold War, the United States intervened directly to bolster Mobutu against armed attempts to overthrow him. But that was in the days when Cuba had troops in Angola and much of Africa was an arena for the U.S.-Soviet struggle. In recent years, however, Washington has increasingly distanced itself from a ruler widely reviled as corrupt, tyrannical and a threat to Zaire's neighbors.

"We have long recognized, at least in the last four or five years, the problems with Mobutu," Secretary of State Madeleine K. Albright said last week. "We have now made it very clear that Mobutuism should {be} and is over."

Kabila, a longtime opponent of Mobutu who had lived mostly in the bush in eastern Zaire for a quarter century, triggered an armed rebellion last year when Mobutu moved to expel ethnic Tutsis who had lived in the region for generations.

In the beginning, the focus of Washington's concern was the fate of tens of thousands of Rwandan refugees -- mostly Hutu, the arch foes of the Tutsis -- who were living in eastern Zaire and threatened by the Tutsi revolt.

The United States and its allies were within days of sending a military force to the region to protect the refugees when the extremist Hutu militiamen controlling the refugee camps suddenly fled the Tutsi advance, enabling most of the refugees to return peacefully to Rwanda.

With the Tutsi-led Rwandan government aiding Kabila's forces, Washington then directed its efforts at containing the conflict, which threatened to engulf much of Central Africa.

But Uganda, Angola and other countries of the region with long-standing grievances against Mobutu supported Kabila anyway, partly because they did not find Washington's messages credible, according to U.S. officials and African diplomats.

The reason is that Uganda and Rwanda in particular were part of a U.S.-supported regional coalition opposed to the fundamentalist Islamic regime in Sudan, and participants in the discussions about Zaire understood that Washington did not want a breach with those countries, officials and diplomats said.

"When we considered how to squeeze Uganda and the others we -- how can I put this delicately?" one senior official said. "We have a common concern about one of their neighbors."

"We have been very transparent about it," said Ugandan ambassador Edith Ssempala. "There were rebels {against Uganda} training in eastern Zaire, it affected us and the Americans understand that."

Ssempala said "in the beginning the Americans expressed a lot of concern about the disintegration of Zaire. When my president {Yoweri Museveni} was here in February, he said that argument was a red herring. He said nobody was working for the disintegration of Zaire." Another Policy Shift

The perception that Washington was less than determined to head off external support for the rebels was reinforced in late March, independent analysts said, when first lady Hillary Rodham Clinton visited Uganda, hailed its economic and social progress and said nothing about its involvement in Zaire.

Washington's strategy shifted again in mid-March, officials said, as Kabila's forces bore down on the key provincial city of Kisangani and it became apparent that the rebels might sweep all the way to Kinshasa and take the entire country by force.

Albright ordered a review of policy options in Zaire and concluded "that this was an opportunity that could possibly strengthen a transition to democracy," State Department spokesman Nicholas Burns said. The new policy, he said, was to "put pressure on Kabila to have an orderly transition and on Mobutu to see the handwriting on the wall."

Kabila, heady with success and backed increasingly by Angola, did not want a cease-fire and negotiations. He insisted that Mobutu quit, and held to those terms even after Clinton sent U.S. Ambassador to the United Nations Bill Richardson to Zaire to seek Mobutu's departure and an orderly transition.

"We didn't want chaos, bloodshed or the breakup of Zaire" in a final battle, a senior administration official said. "It matters to us how it comes out."