Iranians will elect a special commission in December to choose a successor to Ayatollah Ruhollah Khomeini as leader of the Islamic state, Tehran radio said yesterday. The health of Khomeini, 83, reportedly is deteriorating.

The state-run radio said the elections will be Dec. 10 and that men and women 16 years and older are eligible to vote. Iranian sources said the assembly will consist of about 60 members. They said it is unclear whether one successor or a committee of successors would take over should Khomeini vacate the office.

In May, Iran announced that a special succession panel of three to five people would be selected to consider a successor to Khomeini. Yesterday's broadcast did not say what had happened to those plans.

Meanwhile, Iran announced it had rejected an Islamic peace committee proposal submitted Saturday that warring Iran and Iraq withdraw to the borders established by the Algiers accords of 1975. Iraq, which has lost the initiative in the war, announced acceptance of that point among several reportedly submitted to the two sides.

At the start of the war in September 1980, Iraq had denounced the Algiers accords, claiming they had not been respected by Iran. Last June 20, Iraq said it had withdrawn to what it termed "international frontiers" but made no mention of the accords.