Role: Obama administration's special envoy to the Middle East
He was appointed as envoy just two days after Barack Obama was sworn in as the US president, and left for the Middle East within a week of his appointment. He has made more than a half-dozen trips to the region since then, and has met repeatedly with Binyamin Netanyahu, the Israeli prime minister, Mahmoud Abbas, the Palestinian president, and others.
He previously served as the chair of an international fact-finding mission created by Bill Clinton, the former US president. The report offered three suggestions for restarting the stalled Israeli-Palestinian "peace process": a halt to violence; a series of "confidence-building measures," particularly the end to Israeli settlement growth; and a resumption of negotiations.
Mitchell was the chief mediator during the Northern Ireland peace talks held during Clinton's term in office. He chaired the negotiations that led to the Good Friday Agreement.
Mitchell held a variety of roles before being appointed envoy, including three terms in the United States Senate.
Role: United States' Secretary of State between 2005 and 2009 under George Bush
Before her confirmation as Secretary of State, Rice, 56, was Bush's National Security Adviser during his first term.
Rice stated that the September 11, 2001 attacks were rooted in "oppression and despair" and that the US should advance democratic reform and support basic rights throughout the greater Middle East.
Her emphasis on supporting democratically elected governments faced challenges as Hamas captured a popular majority in Palestinian elections in 2006, and influential countries including Saudi Arabia and Egypt maintained authoritarian systems with US support.
Throughout her tenure as Secretary of State, Rice made numerous fruitless attempts to impose the Road Map to peace in the Middle East, a plan originally outlined by Bush in a speech in 2002 in which he called for an independent Palestinian state living side by side with Israel.
Her diplomatic performance in the Middle East and at home in the US earned her the nickname of "Warrior Princess", reflecting strong nerve and delicate manners.
Role: Assistant to President George Bush and Deputy National Security Adviser from January 2001
In Bush's second term, Hadley, 63, replaced Condoleezza Rice as National Security Adviser upon Rice's confirmation as Secretary of State.
As assistant to the president, he admitted fault in allowing a disputed claim about Iraq's quest for nuclear weapons material to be included in Bush's 2003 State of the Union Address.
On July 2003, Hadley offered his resignation to Bush because he had "failed in that responsibility" and because "the high standards the president set were not met." Bush denied his request.
Amid this, The Times of London reported that Hadley was Bob Woodward's source for Valerie Plame's name in the CIA leak scandal, but this report proved to be false when Richard Armitage admitted that he was Woodward's source.
During the administration of George Bush Senior, Hadley was "Pentagon aide to [Under-Secretary of Defence Paul] Wolfowitz," serving as the Assistant Secretary of Defence for International Security Policy from 1989–1993.
In that position, he was responsible for US defence policy towards NATO and Western Europe on nuclear weapons and ballistic missile defence, and arms control.
Hadley is currently Senior Adviser for International Affairs at the United States Institute for Peace in Washington, DC.
Role: Former United States’ Security Co-ordinator for Israel and the Palestinian Authority
Since the summer of 2007, Dayton has been overseeing the formation of the Palestinian Security Forces in the West Bank, a force created to serve the Palestinian Authority in matters of public order and to fight Hamas.
The training of the Palestinian Security Forces takes place in a facility outside of Amman, Jordan - incidentally, the same facility where Iraqi security forces are trained by the US. Each Palestinian battalion contains 500 combat troops. The training programme is prepared together with Israel.
Prior to his assignment in Israel, Dayton spent 37 years in a variety of command and staff assignments. As the director of the Iraq Survey Group, he was closely involved in Operation Iraqi Freedom. He also served as a senior member of the Joint Staff, and as defence attaché in the US embassy in Moscow, Russia.
Dayton has written many articles over the course of his career and was one of the co-authors of The Future of NATO: Facing an Unreliable Enemy in an Uncertain Environment, a study on the future of NATO published in 1991.
Dayton is currently the director of the George C Marshall European Center for Security Studies in Garmisch-Partenkirchen, Germany.
Role: Assistant Secretary of State for Near Eastern Affairs in the United States’ Department of State.
Welch started his diplomatic career as a political officer at the US embassy in Islamabad in 1979 and returned after two years to the State Department where he was desk officer for Lebanon and Syria.
Born in Munich in 1953 to US diplomat parents, Welch has been assigned to a number of embassies throughout the Middle East as head of the political section.
Between 1996 and 1998, Welch served in the State Department's Bureau of Near Eastern Affairs, playing an important role in US foreign policy in Iran, Iraq and Libya.
In August 2001, Welch was appointed US ambassador to Egypt, where he was criticised for acting like an "American High Commissioner in Egypt”, referring to the British High Commissioner during British occupation. Many Egyptians saw his attempts to rid the Egyptian curriculum and religious sermons of anti-Semitism as unwelcome interference in domestic affairs.
As Assistant Secretary of State for Near Eastern Affairs from 2005 through 2008, Welch was closely involved in the negotiations between the Israeli and the Palestinian Authority (PA).
Welch resigned from his position as the top US diplomat in the Middle East in December 2008 to pursue work in the private sector.