JAKARTA, INDONESIA, SEPT. 8 -- Prince Norodom Sihanouk, the leader of one of three Cambodian resistance groups, today begged off attending the opening of a crucial peace conference here but called for a settlement of Cambodia's 11-year conflict based on a plan adopted by the U.N. Security Council.

After Sihanouk sent a message from his exile home in Beijing saying he was too ill to attend, the prime minister of Cambodia's Vietnamese-installed government, Hun Sen, reversed a decision not to participate in the talks himself unless Sihanouk also attended.

Despite gamesmanship and squabbles over protocol, representatives of the four warring Cambodian factions -- Hun Sen's government and the three guerrilla groups -- now are set to open a round of negotiations Sunday that organizers regard as the best chance yet for a breakthrough.

They have been prodded to the negotiating table by the five permanent members of the U.N. Security Council -- the United States, the Soviet Union, China, Britain and France -- who last month reached an unprecedented accord on the Cambodian conflict and issued a plan for a comprehensive settlement involving a massive U.N. military and administrative role.

In a statement prepared for his arrival in Jakarta and released today in his absence, Sihanouk called on the four Cambodian parties to adopt the Security Council's five-part plan as "their sole basic document" and to set up a joint "Supreme National Council" as stipulated in the U.N. plan.

In what he described as a concession, the former Cambodian monarch said the resistance coalition -- comprising the communist Khmer Rouge and two noncommunist groups -- now accepts the government's formula for the council of six representatives each from the government and rebel sides plus a "chairman," who is likely to be Sihanouk. Each rebel group will thus get two members on the council. The resistance, notably the Khmer Rouge, previously had demanded an equal number of seats for each of the four factions.

Sihanouk said the resistance coalition, recognized by the United Nations as Cambodia's legal government, agrees to turn its U.N. seat over to the Supreme National Council, as called for in the Security Council plan. He also said the new body should make decisions "by consensus," rather than by majority vote.

A spokesman for Sihanouk here conceded that his illness was a diplomatic one and said the prince was miffed by criticism of him by Hun Sen on arrival in the Indonesian capital Friday. The spokesman said the prince might show up early next week if there is progress in the talks, in which his faction will be represented by his son, Prince Norodom Ranariddh.

According to Cambodian resistance officials, the main issue to be settled here is whether the Hun Sen administration will accept the U.N. plan in its entirety. If so, the officials said, the delegations can move on to naming a Supreme National Council.

The Phnom Penh government's president, Heng Samrin, has called the plan a "guideline" amid indications of significant reservations about it. Hun Sen told reporters here that "we have already accepted the {U.N.} documents as the framework of a comprehensive solution." He added, "This means it's a basis of the negotiations."

Under the U.N. plan, a Supreme National Council would turn over major powers to the United Nations to permit disarmament of the warring factions and free elections.

To further nudge the Cambodians toward an agreement that would pave the way for implementation of the plan, Secretary of State James A. Baker III on Wednesday announced that U.S. officials would hold direct talks for the first time with the Cambodian government, which Washington has long refused to recognize.

Soviet Foreign Minister Eduard Shevardnadze followed that by announcing Friday in Tokyo that he would soon meet with Sihanouk, a departure from Moscow's longstanding policy. The Soviet Union, the main backer of Vietnam and the Cambodian government, and China, which supports the Khmer Rouge, recently announced an agreement to stop delivering arms to the opposing sides in the conflict.