JAKARTA, INDONESIA, SEPT. 11 -- Weary of war and vulnerable to policy shifts by their superpower backers, leaders of the combatants in Cambodia have accepted a series of compromises that, for the first time, opens the possibility of solving one of the world's most intractable conflicts.

While much could still go wrong in negotiations ahead, the four warring parties recognize that the international climate that has sustained their 11-year war has changed, diplomats and participants in the Cambodian peace talks here said.

With little other choice, the parties thus appear committed to following a course charted for them last month by the five permanent members of the U.N. Security Council -- the United States, China, the Soviet Union, France and Britain.

In their agreement Monday, the Vietnamese-installed Communist government in Cambodia and three guerrilla organizations opposed to it announced their formal acceptance of the big powers' peace plan and formed a 12-member Supreme National Council to represent the four parties as Cambodia's sole "source of authority."

How the council will operate remains unclear, but its role appears largely symbolic, since the peace plan calls for the body to turn over substantial powers to the United Nations as part of a transition to free elections.

Ultimately, the United States and other Western powers hope, the U.N. peace formula and Monday's accord could lead to a neutral, non-Communist Cambodia. After nearly four years of destruction and horror under the radical Communist Khmer Rouge in the late 1970s, and 11 years of continued deprivation and international isolation since then under another Communist government installed by Vietnam, many Cambodians can be expected to opt for a different ideology in a free vote.

More immediately, however, the latest developments in the peace process have ratified the longstanding position of China that -- like it or not -- no solution is possible in Cambodia without the participation of the Khmer Rouge. This is now grudgingly accepted even by Cambodian Prime Minister Hun Sen, whose Hanoi-backed government appears increasingly threatened on the battlefield by some of the world's most hardened guerrillas.

After failing to eradicate the Khmer Rouge in its 1978 invasion of Cambodia and subsequent 10-year occupation, Vietnam also seems resigned to their inclusion in a settlement.

Ironically, it is in the United States that a potential problem looms over Khmer Rouge involvement in a settlement. Amid congressional pressure and fears of Khmer Rouge military gains in Cambodia, the Bush administration in July announced it was withdrawing U.S. recognition in the United Nations of a three-party resistance coalition that includes the Khmer Rouge.

However, the Supreme National Council formed here in part to take over the coalition's U.N. seat includes two Khmer Rouge leaders among its 12 members. They are Khieu Samphan, the organization's prominent political figure and the intellectual author of the radical policies implemented by former dictator Pol Pot, and Son Sen, the current Khmer Rouge military commander and a close Pol Pot associate.

Participants in the talks said the four parties decided to let each name its own delegates to the council to avoid an impasse after agreeing on a formula for the body. The Phnom Penh government has six of the council seats, and the three resistance parties have two each. Left open was the possibility of inviting Prince Norodom Sihanouk, who heads one of the three resistance groups, to become the council's chairman and 13th member.

Secretary of State James A. Baker III said in July that he saw a "significant difference" between Khmer Rouge involvement in the resistance coalition and the proposed Supreme National Council, but aides conceded that the presence of Khmer Rouge leaders on the council could reignite congressional criticism. "They {the four Cambodian parties} obviously threw Western sensibilities to the wind," a senior White House aide said Monday of the Khmer Rouge membership on the council.

"We could not avoid it," said Son Sann, the leader of the anti-Communist Khmer People's National Liberation Front, the smallest resistance party. In an interview today, he said the high-level Khmer Rouge participation suggests that the organization attaches importance to the council and that its delegates will have the clout to make guerrilla commanders on the ground abide by the peace plan.

"If we exclude the Khmer Rouge from the Supreme National Council, it means we exclude them from the peace process, and then how can we get peace?" asked Pol Ham, a Son Sann aide.

"We have to put personal feelings aside at this moment . . . or we will never end up with anything at all," said Uch Kim An, director of policy in the Cambodian Foreign Ministry. He said his delegation had not objected to the naming of Khieu Samphan and Son Sen, even though both are on a government "blacklist" of Khmer Rouge leaders subject to trial for "crimes against humanity."

Non-Communist participants in the talks point out that at least four of the Phnom Penh government's delegates to the council, including Hun Sen himself, are former Khmer Rouge members who broke with the group in a split between its pro-Chinese and pro-Vietnamese factions. Hun Sen, 39, joined the movement as a teenager and rose to the rank of Khmer Rouge regimental commander before joining the Vietnamese side. Hor Nam Hong, a Phnom Penh government minister named to the council, has been blamed by Sihanouk for the deaths of several of the prince's relatives while Hor Nam Hong was running a reeducation camp during Khmer Rouge rule in Cambodia. Two other council members who were once Khmer Rouge members are Tie Banh, defense minister in Hun Sen's government, and Sin Song, now interior minister. Correspondent Keith B. Richburg in Washington contributed to this report.