A breakthrough was reached today in a prolonged diplomatic debate between the five-member Association of Southeast Nations and China on a proposal to end the fighting in Cambodia and pave the way for free elections, according to diplomatic sources.

The diplomatic wrangle ended when China agreed to endorse a compromise version of a U.S.-supported ASEAN draft declaration on the fourth day of talks among 83 nations attending a U.N.-sponsored conference to map a strategy for getting Vietnam to pull its troops out of Cambodia.

Neither Vietnam nor the Soviet Union is attending the conference, and Hanoi has said it will not recognize any of its pronouncements.

According to diplomatic sources, a final resolution will be adopted by the full U.M. General Assembly conference Friday. It will include a call for "appropriate arrangements to ensure that armed Kampuchean [Cambodian] factions will not be able to prevent or disrupt the holding of free elections."

Negotiations on the wording of the conference resolution stalled earlier in the week when China objected to an ASEAN proposal that called for disarming all the conflicting forces in the country and setting up an interim government in advance of free elections.

China, which supports the Pol Pot government that Vietnamese forces overthrew when they invaded Cambodia in December 1978, opposes the disarming of Pol Pot's 30,000-member guerrilla force.

China also raised objections to the establishment of an interim government, presumably because it would dilute the Pol Pot forces' claim on the right to govern the country.