A meeting of 18 foreign ministers and international relief officials today sought to launch the United Nations-led effort to administer and rebuild Kosovo, but found itself divided on key issues, including whether some reconstruction aid should be directed to Serbia.

The four-hour gathering led by U.N. Secretary General Kofi Annan here dramatized the unprecedented scope of the U.N. commitment in the battered province. Big questions -- including the cost of rebuilding Kosovo, the time it would take, and how to handle the rebel Kosovo Liberation Army -- went unanswered. And so did smaller questions, such as what currency Kosovo will use, who will run the schools and courts, and who will be in charge of the U.N. civilian administration.

Annan, U.S. Secretary of State Madeleine K. Albright and other representatives of the Group of 8 industrial countries, Security Council members and several international organizations said after the meeting that they were encouraged by pledges of support, including the commitment of 1,900 international police by U.N. members to keep order in the province.

But the officials said they also recognized that the United Nations has assumed unprecedented responsibilities as the de facto sovereign power in Kosovo. Not even in Somalia -- where many analysts thought the U.N. developed a permanent distaste for "nation building" during an ill-fated intervention in the early 1990s -- did the United Nations take on such a broad range of government tasks.

"There clearly is a huge challenge ahead of us," Albright said. "The military part of the campaign was only the beginning of what is a very long-term and difficult proposition."

"The water, the power, the sewage, the schools, the hospitals, [the U.N. civilian administration] is going to have to do everything," another U.S. official said.

Despite statements affirming their unanimity of purpose, it was apparent that the ministers encountered difficulty in deciding on specific issues they now face as governors of a territory.

Even the basic question of whether to arm the U.N.-sponsored police force produced disagreement. U.S. and Canadian officials said the police will have to be armed because Kosovo remains violent and dangerous, but Annan said some countries will not contribute to the force if members carry weapons.

Albright said the United States will contribute 450 officers to the planned 3,100-member international police force. Annan appealed to those who made the pledges to send the participants "as urgently as possible."

Canadian Foreign Minister Lloyd Axworthy and U.N. officials stressed the urgency not only of establishing the interim civilian administration, but of moving ahead with political arrangements for Kosovo self-government. They said those moves were needed to prevent the development of a vacuum that could be filled by the Kosovo rebel army.

"It has to start right now," Axworthy said. "Political authority cannot be usurped by one group."

The desire to prevent the Kosovo Liberation Army from seizing exclusive political control will be reflected in the composition of a 1,000-member Kosovar police force to be recruited and trained over the coming year. Individual members of the KLA will be allowed to apply for positions on the force, a senior U.S. official said, but they will have to compete with other applicants and sever their ties to the rebel army.

A senior U.S. official said the time guidelines set down in the abortive Rambouillet peace agreement last winter, calling for province-wide elections in a year and municipal elections even earlier than that, are "realistic." Annan, however, said the mission "is going to take a while" -- perhaps as long as 10 years.

Annan said he wants to ensure that the "humanitarian needs" of the people of Serbia are attended to as well, but there he encountered some resistance. The United States, Britain and Germany restated their opposition to any reconstruction aid to Serbia so long as Slobodan Milosevic is its leader, participants said. They accepted the principle of humanitarian assistance, one senior official said, but wanted it narrowly defined so as not to benefit Milosevic.

Annan said he hopes to choose a full-time civilian administrator for Kosovo by the end of the week. The candidates are French cabinet minister Bernard Kouchner, Dutch minister Jan Pronk, British politician Paddy Ashdown and European Union commissioner Emma Bonino.