Ayatollah Ali Khamenei, the supreme leader of the Islamic Republic, wields the greatest religious and political power of anyone in Iran. The leader, whom many consider a hard-line conservative, was chosen by an assembly of senior clerics (the Assembly of Experts) to succeed the late Ayatollah Khomeini, founder of the Islamic Republic of Iran and Khamenei's early mentor, in 1989.

Before that, Khamenei was president for two terms, from 1981-1989. Following President Mohammad Rajaee’s assassination in 1981, Khamenei was elected president with a 95 percent vote.

From 1981 to 1985, he also served as head of the Supreme Defense Council and the Supreme Cultural Revolution Council.

Early in life, however, the future leader aspired to follow in his father's footsteps as a religious scholar.

Born in the holy city of Mashhad, Sayyid Ali Khamenei was raised in a poor household by a father who, as he later describes in his autobiography, was "a well known religious scholar who was very pious and a bit of a recluse."

In 1952, at the age of 21, Khamenei began attending lectures by "the great revolutionist and Martyr Sayyid Mujtaba Nawwab Safawi, who spoke about reviving Islam and its Divine Rule and warned the Iranian people of the deceitful lies of the Shah and the English government." That year marked the beginnings of his political aspirations that would propel him throughout his life.

In 1958, while continuing his studies at a seminary in Qom, located in central Iran, Khamenei became a disciple of Ayatollah Khomeini and deepened his participation in the anti-shah Islamic movement. Between 1963 and 1976, the shah's secret police, or Savak, arrested Khamenei at least a half dozen times for his leadership of clandestine political operations.

As a young radical, Khamenei fought to create a new future for his country and to free Iran from what he saw as a corrupt government beholden to U.S. interests.

He and other radical clerics, including Khomeini, in 1977 formed the Combatant Clerics Association, which became the foundation for the Islamic Republic Party. By January 1979, with the shah ousted from power, Iran's new supreme leader Ayatollah Khomeini named his longtime cohort Khamenei a member of the Revolutionary Council.

Under Iran's constitution, Khamenei has the authority to override every other member of the government. He can confirm and dismiss a sitting president, a law that has provoked instability and power struggles between Khamenei and other political leaders.

Indeed, Khamenei has shown intolerance toward anyone questioning his strident anti-West and fundamentalist Islamic policies.

For instance, in 1997, Ayatollah Hossein Ali Montazeri, a high-ranking cleric and scholar once designated successor of Ayatollah Khomeini, criticized Khamenei's rule, calling the supreme leader incompetent. Khamenei immediately placed the cleric under house arrest for five years.

Montazeri was not alone in his call for greater democratic changes in the Islamic state. Kenneth Timmerman, executive director of the non-profit human rights organization Foundation for Democracy in Iran, told the NewsHour on Dec. 15, 1997: "There’s an incredible fight going on inside the traditional clergy between Khamenei, the supreme leader, who represents this radical anti-Western, anti-American faction, which has a certain popularity, and another faction which says, enough is enough ... let’s have a regime and a government which is more democratic and more open to the West. The arrest of Ayatollah Montazeri ... is extremely important ... I think you could have an explosion inside Iran."

Such challenges to the supreme leader's authority further intensified with the landslide victory of reform-minded President Mohammad Khatami in the 2001 presidential election. Analysts from the International Crisis Group say the battle brewing between Khatami and Khamenei represents a broader, and potentially volatile, divide between the country's conservative Islamic establishment and a growing number of pro-democracy Iranians, many of whom were born after the 1979 Iranian Revolution and never experienced the oppressive regime of U.S.-backed Shah Mohammad Reza Pahlavi.

Yet not all Iranian government leaders believe the new reformists can ease Khamenei's hard-line policies.

As Ebrahim Yazdi, a liberal opposition leader, explained: "Khatami won only the presidential election, that's all. The extreme right lost the election, but they control all the powers: parliament, radio and television, the security forces, the supreme leader's institutions, the Friday prayers preachers."

Indeed, Khamenei maintains his grip on power with support from influential clergy members, the powerful Guardian Council, his loyalists in the Parliament. Iran's wealthy business owners must answer to Khamenei and are exempt from paying taxes to his government. Khamenei selects the heads of Iran's security forces. He also maintains strict control over Iran's media, and regularly censors or shuts down independent newspapers and informational Web sites.

Khamenei also has ultimate decision-making authority over foreign policy matters. While many younger Iranians are eager to improve economic and cultural relations with the United States, Khamenei has made clear his opposition to U.S. policy, and firmly rejects holding any talks with U.S. representatives.

During the pro-reform student protests in June 2003, Khamenei immediately warned that such actions would not be tolerated. He also blamed the United States for provoking the demonstrations.

"Leaders do not have the right to have any pity whatsoever for the mercenaries of the enemy," he said in a televised speech.

Yet, despite Khamenei's grip over his conservative Islamic state, the ayatollah does appear to recognize that Iran's political climate is changing, according to a 2002 report from the International Crisis Group, entitled "Iran: The Struggle for the Revolution's Soul."

In the 2000 general elections, Khamenei loyalists lost their dominance in the Parliament to the reformists, who won 226 of the 290 parliamentary seats.

Some analysts speculate Khamenei may realize that it is in his and the influential clergy's interest to allow a controlled, gradual economic and political liberalization, rather than risk a social explosion. There are some indications that Khamenei may slowly concede to certain moderate reforms.

Following his release from house arrest, the government allowed Montazeri, the top dissident cleric, to resume his public lectures. In an August 2003 public speech to some 300 students, the top dissident cleric called for "a popular vote" for the ruling government.

"If people are not satisfied, the establishment is not legitimate," Montazeri told the Associated Press in August 2003. "The authorities should increase their tolerance ... and allow the new generation to choose its future."

-- Compiled by Liz Harper for the Online NewsHour