NICOSIA, Cyprus (AP) _ President Ali Khamenei is Iran's caretaker leader, but the true successor to the late Ayatollah Ruhollah Khomeini has yet to be chosen.

The transfer of power may be resolved Aug. 18, when a presidential election is scheduled in tandem with a referendum on constitutional changes aimed at eliminating a system of competitive power centers that has snarled decision- making.

Khamenei, 49, was chosen Sunday by the 83-member assembly formed after Khomeini's fundamantalist Shiite Moslem revolution in 1979 to determine the succession and write the new constitution.

Khamenei acknowledged his temporary role and said that, when the constitutional changes have been ratified, ''we should be able to fill the vacuum'' caused by Khomeini's death.

Reports from Tehran indicate Iran will have a collective leadership of three to five men in the absence of a single figure with Khomeini's religious and political authority.

In order for that to happen, the 20-member committee Khomeini assigned to reform the constitution will have to change the religious requirements for leadership to allow lower-ranking figures to participate.

Most analysts believe the power struggle of rival factions and leaders will intensify.

Here are sketches of the main candidates for a collective leadership:

-Hashemi Rafsanjani: The 55-year-old speaker of parliament, a middle- ranking cleric, also is military commander-in-chief. Rafsanjani is a member of the Supreme Defense Council, deputy chairman of the Assembly of Experts and sits on other important bodies.

He is a skilled political operator with a wide power base that includes parliament and the Revolutionary Guards Corps, and leads the so-called pragmatists in the hierarchy.

With Khamenei's support, Rafsanjani sought to improve relations with the West and end Iran's isolation. He was a key figure in persuading Khomeini to accept the U.N.-sponsored cease-fire that halted fighting in the 8-year-old war with Iraq last August.

Rafsanjani and his allies were set back by the radical resurgence that followed the outcry over Salman Rushdie's novel, ''The Satanic Verses.'' He is the only declared candidate for president.

-Ali Akbar Mohtashemi: The interior minister, 43, is among the most radical hardliners. As ambassador to Syria in 1981-1985, he was closely linked to the Shiite fundamentalist Hezbollah, or Party of God, in Lebanon and considered by Western Intelligence to have masterminded suicide bombings of American, French and Israeli targets.

He heads much of Iran's security apparatus and appointed most of the 24 provincial governors.

-Hussein Musavi: The prime minister, 48, is a radical who has led the government since 1981. He sits on the 12-member Council of Guardians, which is dominated by conservatives and oversees all legislation, and is a member of a special Expediency Council appointed by Khomeini in 1988 to resolve differences between the parliament and Council of Guardians.

Musavi been criticized, mainly for economic policy, but survived three confidence votes, largely through Khomeini's support. He is opposed by conservative clerics and the business class but has the support of powerful hard liners.

-Ayatollah Ali Meshkini: The radical chairman of the Assembly of Experts, 66, is a ranking Islamic jurist and leader of sabbath prayers in the holy city of Qom, which gives him an important platform. He is the father-in-law of Intelligence Minister Mohammad Mohammadi Rey-Shahri, another major hardliner.

-Musavi Khoeiniha: The prosecutor-general, 47, is anti-Western and known as ''the red mullah'' because he studied at Patrice Lumumba University in Moscow and Leipzig University in East Germany.

He was removed as head of the pilgrimage bureau for inciting pilgrims visiting the shrines of Mecca and Medina in Saudi Arabia to violence and to spread Iran's revolution.

Khoeiniha was the political leader of student ''followers of the imam's line'' who stormed the U.S. Embassy in 1979. He is a leading member of the Society of Combatant Clergymen, a powerful radical group, and supports Hezbollah, which is considered an umbrella for Shiites holding most of the Western hostages in Lebanon.

-Ahmad Khomeini: The late patriarch's son, 43, has wielded considerable political influence behind the scenes. He holds no office, but controlled access to his increasingly reclusive father and now is making an open bid for power. He formerly was allied with Rafsanjani, but now is aligned with Mohtashemi and the hard liners.

Mohammad Mohammadi Rey-Shahri: The 43-year-old intelligence minister has emerged as a powerful figure in recent years. He is a middle-ranking cleric allied with Mohtashemi and the hard liners opposed to Rafsanjani, and formerly served as a judge in the military revolutionary tribunals.

-Ayatollah Abdulkarim Musavi Ardebili: The chief justice, 63, is a centrist and member of the special assembly appointed by Khomeini in 1988 to resolve differences between the parliament and Council of Guardians.