A few months ago, Ramush Hajredinaj was moving his headquarters from farmhouse to farmhouse a few miles east of here, and his only concern was killing Yugoslav troops. Now, the commander of rebel forces in southwestern Kosovo receives visitors from behind a polished wooden desk in the sole intact office building in this devastated city, and his daily preoccupations are reopening bakeries and hospitals.

"We are taking care of every problem for the future," says Hajredinaj, who is renowned here for his aggressiveness on the battlefield. "If we wait for the international community, we will have to wait too long. They are a little bit slow."

Hajredinaj is one of the many leaders of the ethnic Albanian Kosovo Liberation Army who have moved to seize the instruments of power in this Connecticut-size Serbian province, making an enthusiastic transition from the mountains and fields where they lived on the run for 16 months into new, KLA-mandated jobs as mayors, police chiefs and administrators of a shattered society.

Without taking off their uniforms, the rebels have filled the streets of six of Kosovo's seven largest cities, taken over the best offices in Kosovo's few intact buildings and hung the Albanian flag outside dozens of police stations.

The rebels also have begun to compete with NATO troops as the ultimate guarantors of law and order amid the postwar chaos in Kosovo. The KLA formally agreed with NATO early today to stop carrying small arms in many areas of the territory and to put its heavy weapons in storage within 30 days, but the rebels have said repeatedly in recent days that the agreement will not represent the last word on whether they will eventually seek to create a home-grown army in Kosovo.

Western officials here have been startled by the guerrillas' move to take the helm of nascent civil structures being formed in Kosovo, and they are uneasy about it.

A long-held Western objective in Kosovo is to drain away the organization's militant spirit by integrating its leadership into more moderate ethnic Albanian political structures. The strategy is meant in turn to make the KLA more vulnerable to Western and democratic pressures and undermine the group's demand for Kosovo's independence from Serbia, Yugoslavia's dominant republic. In little more than a year, however, the KLA leadership has managed not only to become an accepted part of Kosovo's political system, but also to usurp virtually all its power.

This change was dramatized by the provisional government established this spring by KLA political leader Hashim Thaqi, who chaired the ethnic Albanian delegation at unsuccessful peace talks with the Serb-led Yugoslav government in France earlier this year.

Thaqi's provisional government does not include Ibrahim Rugova -- a pacifist who supports nonviolent opposition to Serbian rule -- who was reelected last year as president of Kosovo's unofficial ethnic Albanian administration. The KLA's dislike of Rugova intensified when he met with Yugoslav President Slobodan Milosevic during the war; Rugova has said since that he attended the meeting under duress, at a time when his family was under house arrest in Pristina, the Kosovo capital.

But Rugova still commands some respect among Kosovo's elderly, and, in the past month, he has repeatedly spurned offers by Thaqi to heal their divisions by forming a coalition government with the KLA at the helm. Instead, the two men have competed to make the first public appearances at ethnic Albanian refugee camps in Macedonia and Albania, and this week both are vying to be the first to make a public statement in Pristina since the end of the war.

The KLA has established its political ascendancy partly by depicting itself as the triumphant guardian of ethnic Albanian security -- despite its frequent battlefield losses in the face of superior Yugoslav army firepower. The KLA's name is written everywhere in graffiti, and the most popular current songs among ethnic Albanian children are hymns to its military prowess.

The rebels are filling a vacuum created by the current flight from Kosovo of tens of thousands of Serbs, who had occupied virtually every important government-related job here since 1989. That was when Milosevic stripped Kosovo of the broad autonomy it held under the old six-republic Yugoslav federation and elevated the prerogatives of Serbs over those of ethnic Albanians, who accounted for 90 percent of the province's prewar population. As a result, many thousands of ethnic Albanians were summarily fired from government jobs.

KLA officials say they will abide by NATO's instructions, including the alliance's demand for equal treatment of Kosovo's Serbs and Albanians. But they also express no regrets at the flight of so many Serbs -- most of them fearing reprisal from ethnic Albanians persecuted by the Belgrade government. "They have a right to go," said Rustem "Remi" Mustafa, 28, a KLA commander in a north-central zone of Kosovo that includes Pristina. "During this war, they weren't indifferent. They robbed, looted and burned their neighbors. . . . Maybe they should feel worried for their security. Somebody from the civilian population could try to seek revenge."

Civil administration -- including such tasks as organizing an election, collecting trash and issuing marriage licenses -- is supposed to be controlled by the United Nations under the June 10 Security Council resolution that authorized deployment of the NATO peacekeeping force. But, observed Veton Surroi, who edits the ethnic Albanian newspaper Koha Ditore: "I don't see the civil authority being established anywhere."

A 30-member U.N. mission that reports to Secretary General Kofi Annan opened an office in Kosovo yesterday. Fabrizio Hochschild, an adviser to the chief of the mission, said the powers the United Nations was given "came as something of a surprise" and noted that the mission has "no standby assets."

He said that U.N. officials are not surprised by the KLA's assumption of power and that they have agreed they "will welcome anything undertaken by any Kosovar that contributes to the rule of law. If anyone takes over by opportunism or force . . . to try to set up fiefdoms, then we will in consultation with [NATO] . . . to try to stop that." Hochschild added that the KLA should understand that any arrangements it makes now are "interim" and will continue only if they prove they "are legitimate -- meaning democratic."

Here in the western city of Pec, the KLA has stepped into a vacuum created by Italian NATO soldiers, who have yet to take an activist policing role, according to several officials with humanitarian organizations. They said KLA members shot several Serbs who were burning a row of houses after KLA commanders complained to Italian troops and got no response.

The KLA also has been tracking shipments of humanitarian aid to the area and helping keep watch over a warehouse in which such supplies are stored. But an Italian army officer, Lt. Col. Franco Rossi, head of NATO's civil-military center in the area, said he understands that "our main task is the protection of the Serbian people" and that taking on any administrative or engineering functions is "not our responsibility in the first phase" of the NATO peacekeeping mission, which will last another two weeks.

Mustafa, who has established his new headquarters in the hillside Pristina home of a wealthy ethnic Albanian, said he has no doubts about the future course of Kosovo's government and that he expects its police force to be formed "in general with people from the KLA." He said its chief will be a KLA officer and that some KLA members are likely to "go into politics, and some into state administration."

Asked which government ministries he expects the KLA to control, Mustafa listed those concerned with "the control of economic resources, finances and the post office." He added that this should come as no surprise, since "the government now is KLA."

In the southern city of Kacanik, regional KLA commander Xhabir Xarku -- a former restaurant leasing agent in Greenwich, Conn. -- occupies the most imposing office in the police station, one with a curving, glass-topped desk. His men have been scouting the area for land mines and trying to restore electricity and water service.

"I called my wife and told her this is the day I have dreamed of all my life," said Xarku, 34. "Two days ago was the end of the war between freedom fighters and the [Yugoslav army]. But for Albanians, this is the start of another war, the cold war for independence, without arms in our hands. We believe we are going to win in that war, because, after all the Serbs did, we have a right to independence."

CAPTION: KLA political leader Hashim Thaqi heads provisional government.