BANGKOK, SEPT. 19 -- The first meeting of a national unity council that is to serve as an interim government in Cambodia broke up in disagreement today, setting back the effort to end the nation's civil war.

Participants said the chief issues dividing the warring factions within the Supreme National Council were the makeup of Cambodia's delegation to the United Nations and the role former Cambodian monarch Norodom Sihanouk would play in the government. Terms of a formal cease-fire between the Vietnamese-installed government in Phnom Penh and the three-party resistance alliance were not discussed, spokesmen for both sides said.

"I can't believe we've gone so far to break over such little things," said an Asian diplomat close to the negotiations. He and other analysts said it was too soon to tell if the U.N.-sponsored peace initiative that brought the combatants together had been seriously damaged, especially given intense international pressure on the parties to reach a settlement.

Negotiators for both sides indicated they believe the breakdown will be short-lived. Cambodian Premier Hun Sen expressed regret that no agreement had been reached, but he added that "it's only a temporary adjournment." A spokesman for the guerrilla alliance said the talks could resume within days.

The Supreme National Council, as set up under a sweeping peace plan formulated by the five permanent members of the U.N. Security Council, consists of six government representatives and two from each of the three allied guerrilla groups -- the Marxist Khmer Rouge, the National Liberation Front under former premier Son Sann, and forces loyal to Sihanouk.

Under the plan, the council would be the sole source of authority in Cambodia until national elections can be organized, but it would cede many powers to a U.N. interim administration and peace-keeping force that would guarantee the transition to democratic rule.

The guerrilla coalition wants Sihanouk as the council's 13th member and chairman, who conceivably could break a tie vote. Hun Sen has said he could accept Sihanouk as chairman, but not as a voting member.

Resistance sources said a deal had been discussed under which Sihanouk would become council chairman and a voting member if Hun Sen were chosen to lead Cambodia's U.N. delegation, but that other resistance representatives balked.

The guerrilla alliance currently holds Cambodia's U.N. seat, and Son Sann said today that if the guerrillas were to allow Hun Sen to lead the U.N. delegation, "we accept the fait accompli of the occupation of Cambodia by the Vietnamese. We cannot accept that when we have fought for 11 years to liberate our country."