Factbox: Mohamed ElBaradei: Opposition leader and diplomat

Here are some facts about the 68-year-old:

* BID FOR THE PRESIDENCY:

-- ElBaradei returned to Egypt in February 2010 to an exuberant welcome from supporters who hoped he would stir up Egyptian politics by running for president in 2011. Days after retiring from the International Atomic Energy Agency (IAEA), ElBaradei had said a decision on entering the presidential race would depend on guarantees of a fair election.

-- He laid out some conditions for mounting a campaign, including a demand for a new constitution that would better respect human rights and put checks on power.

-- Last June he called on supporters to campaign for a change in the constitution to allow a democratic succession to President Hosni Mubarak. Up to 3,500 Egyptians rallied in Fayoum, south of Cairo, to support him.

-- He said in September 2010 that the leadership of the country would change in the next year and called for a boycott of parliamentary polls last November as they would be rigged.

-- ElBaradei said last week it was time for Mubarak to go. On January 30, ElBaradei put pressure on the United States to support calls for Mubarak to step down, saying "life support to the dictator" must end and dismissed U.S. calls for Mubarak to enact sweeping reform in response to the mass protests.

* LAW AND DIPLOMACY:

-- ElBaradei was born on June 17, 1942, in Cairo. He studied law, graduating from the University of Cairo and the New York University School of Law.

-- He began his career in the Egyptian diplomatic service in 1964, working twice in the permanent missions of Egypt to the United Nations in New York and Geneva, in charge of political, legal and arms control issues.

-- From 1974 he was a special assistant to the Egyptian foreign minister and was a member of the team that negotiated the peace settlement with Israel at Camp David in 1978. He joined the United Nations two years later.

* IAEA CAREER:

-- ElBaradei joined the IAEA in 1984 and became its director-general in 1997. He transformed the IAEA into a body not afraid to take a stand on big political issues relating to peace and proliferation. Critics said that was not its place.

-- ElBaradei was outspoken on the lack of evidence of weapons of mass destruction in Iraq before the U.S.-led invasion in 2003, which angered the Bush administration.

-- While he was IAEA chief, a secret nuclear program was uncovered in Iran. Tehran says the program is peaceful and has ignored U.N. Security Council resolutions demanding it suspend uranium enrichment, the process that can make fuel for atomic power plants or, if done to a very high level, the fissile core of a nuclear bomb. -- ElBaradei retired after 12 years heading the IAEA in November 2009. In 2005, ElBaradei and the IAEA were awarded the Nobel Peace Prize.

Sources: Reuters/www.achievement.org/nobelprize.org

(Writing by David Cutler, London Editorial Reference Unit;)