Vietnam today rejected a proposal by Cambodian resistance leaders to settle the seven-year-old conflict in Cambodia through a two-stage withdrawal of Vietnamese troops and installation of a four-party coalition government.

The proposal was issued in Peking on Monday in the form of an eight-point peace plan advanced by Prince Norodom Sihanouk and his two partners in a resistance coalition that is battling the Vietnamese occupation of Cambodia.

Sihanouk heads the coalition, which is recognized by the United Nations as Cambodia's legal government but which has been spurned by Vietnam and its protege government in Phnom Penh under President Heng Samrin.

The other two partners in Sihanouk's coalition are the Khmer Rouge, headed by Khieu Samphan, and the Khmer People's National Liberation Front led by Son Sann.

According to diplomats in Bangkok, the major change in the new peace plan from previous positions is the acceptance by the Khmer Rouge and Son Sann's group -- and the resistance's main backer, China -- of a coalition that would include the Heng Samrin regime.

Sihanouk long has urged the resistance coalition to work for such a four-party solution, but his partners have resisted any move that might be seen as de facto recognition of Heng Samrin.

On the other hand, both Vietnam and the Hanoi-installed government in Phnom Penh have refused to deal with the Khmer Rouge, ruling out the solution envisaged by Sihanouk.

Vietnamese officials in Hanoi and Bangkok repeated that refusal today, effectively rejecting the new peace plan.

The Agence France-Presse news agency quoted an authoritative source in Hanoi as saying the proposal was unworthy of consideration because it aimed to legitimize Sihanouk's coalition government and effectively restore the Khmer Rouge to power. The Khmer Rouge, led by Pol Pot, ruled Cambodia brutally from 1975 until they were ousted by the invading Vietnamese in January 1979.

A Vietnamese Embassy spokesman in Bangkok also signaled rejection of the peace plan today when he said that Hanoi "will have nothing to do with the so-called coalition government" of Sihanouk.

The plan essentially calls for the following:

*Negotiations with Vietnam, and possibly other countries, on the withdrawal from Cambodia of an estimated 160,000 to 180,000 troops;

*A cease-fire during which Vietnam would withdraw its troops in two stages;

*U.N. supervision of the cease-fire and withdrawal;

*Negotiations after the first stage of the pullout between the resistance coalition and the Heng Samrin regime on establishing a "quadripartite government" with Sihanouk as president and Son Sann as prime minister;

*Free elections supervised by U.N. observers;

*Restoration of an independent, neutral and nonaligned Cambodia without the presence of foreign troops;

*Foreign aid for reconstruction.

A senior Western diplomat called the plan "realistic," but added, "I don't think anything will come of it." He noted that in addition to including the Heng Samrin regime in negotiations, it introduced the idea of a two-phase Vietnamese withdrawal as an enticement and dropped any reference to U.N. resolutions that are more rigid in calling for a complete Vietnamese pullout.

The plan also demonstrates Sihanouk's support for Son Sann, who has been embroiled in a power struggle with the military arm of his resistance group. Diplomats said an effective compromise has recently been reached in which Son Sann will continue to run political affairs while leaving the military side in the hands of officers led by Gen. Sak Sutsakhan.

With the Vietnamese continuing to resist dealing with the coalition, diplomats say the earliest any changes in attitude might emerge would be after a Vietnamese Communist Party congress scheduled for November or December.