Profile: Ayatollah Ali Khamenei
Ayatollah Ali Khamenei is Iran's spiritual leader and highest authority. He has the final say over all political affairs in Iran.
Widely regarded as the figurehead of the country's conservative establishment, Ayatollah Khamenei has repeatedly denounced the West and in particular the United States.
Although he has maintained support for his country's team of negotiators, Ayatollah Khamenei has frequently declared his pessimism about the outcome of discussions with world powers over Iran's disputed nuclear programme.
Ayatollah Khamenei succeeded the original Supreme Leader and founder of the Islamic Republic of Iran, Ayatollah Khomeini, in 1989. Before that he was president for two successive terms from 1981-1989.
In September 2014, Ayatollah Khamenei, 75, underwent prostate surgery in Tehran. An announcement about the surgery ahead of the procedure was unprecedented, as the Ayatollah's health is traditionally a confidential subject.
Seven years earlier a rumour of the Ayatollah's death spread in Iran and the world, simply because he did not announce he had a bad case of flu and could not attend public ceremonies.
When he was president, Ayatollah Khamenei was often at odds with the then prime minister, Mirhossein Mousavi, whom he perceived as being left-leaning.
However, as Mr Mousavi had the backing of Supreme Leader Ayatollah Khomeini, their conflicting views on economic, social and religious policies were left to fester.
One of Ayatollah Khamenei's first decisions on becoming Supreme Leader following the death of Ayatollah Khomeini was to revise the constitution and abolish the post of prime minister.
Ayatollah Khamenei has been noted as lacking the charm and popular support of his predecessor.
Khomeini was a cleric of the highest rank, a Source of Emulation. When Ayatollah Khamenei - not a Source of Emulation - took over, the constitution had to be amended to allow the post to be held by a lower-ranking theologian.
He cemented his position as Supreme Leader by developing networks in Iran's various institutions and security forces, particularly the powerful Islamic Revolution Guards Corps (IRGC).
In 1997, he famously clashed with Ayatollah Hossein Ali Montazeri, a respected and at the time more senior scholar.
Ayatollah Montazeri, a leading dissident who died in 2009, questioned the powers of the Supreme Leader. This led to the closure of his religious school, an attack on his office in Qom and a period of house arrest.
Ayatollah Khamenei's decision-making also came in for criticism. When he sided with former President Mahmoud Ahmadinejad, following the latter's victory in the disputed election in 2009, many Iranians took to the streets in protest at the results.
Defeated candidates Mirhossein Musavi and Mehdi Karroubi challenged the election results. Both were put under house arrest in February 2011, along with Mr Musavi's wife Zahra Rahnavard, after they called for street protests in solidarity with pro-democracy movements in Egypt and Tunisia.
As Supreme Leader, Ayatollah Khamenei has the power to directly and indirectly select members of the Guardian Council. The council is in charge of both the supervision of elections and the vetting of candidates.
In the 2004 elections, the council disqualified thousands of parliamentary candidates including many moderates, reformists and members of the previous government. Conservatives won 70% of the vote.
In 2013, the council blocked Akbar Hashemi-Rafsanjani, the former president and head of Iran's influential Expediency Council, from running for president on grounds of old age. Mr Rafsanjani had sided with protesters after the 2009 election.
Ayatollah Khamenei has consistently backed the supervisory role of the conservative Guardian Council, despite criticism that the disqualifications distort Iranian democracy.
In his inaugural presidential address in 1981, Ayatollah Khamenei set the tone for his leadership by vowing to stamp out "deviation, liberalism, and American-influenced leftists".
In 2009, when US President Barack Obama offered Iran a "new beginning" of diplomatic engagement, Ayatollah Khamenei's response was muted. He said he had seen no change in America's attitude or policy, singling out US support for Israel and sanctions against Iran.
But he said that if President Obama altered the US position, Iran was prepared to follow suit.
In 2013, ahead of nuclear negotiations between Iran and world powers, Ayatollah Khamenei said he was "not opposed to diplomacy", adding that he favoured "heroic flexibility". In language not usually associated with him, Ayatollah Khamenei spoke of diplomacy being the domain of "smiling, asking for and engaging in negotiations".
In November 2013, Iran and the world powers reached an interim nuclear deal, where the Islamic Republic agreed to curb its nuclear programme, in return for partial sanctions relief.
But on 7 July 2014, just two weeks before an initially agreed deadline to finalise a comprehensive nuclear deal, Ayatollah Khamenei made a public address rich with technical detail, stressing that Iran needed to significantly increase its uranium enrichment capacity.
The July deadline was missed and the two sides agreed to extend talks until November 2014.
During and after the US-led war on Iraq, Khamenei was sharply critical of Washington's policies. "The occupation of Iraq is not a morsel that the US can swallow," he said.
In June 2014, after militant jihadists of Islamic State (IS) captured swathes of northern Iraq, Ayatollah Khamenei again opposed US intervention in Iraq. But in August, he welcomed the appointment of Haydar al-Abadi as Iraq's new prime minister, cutting off support for Iran's former ally Nouri Maliki.