"I believe firmly that there’s no such thing as conflict that can't be ended," Mitchell said in a speech to foreign policy experts in Washington in May last year.
"They’re created, conducted, and sustained by human beings. They can be ended by human beings. No matter how hateful, no matter how hurtful, peace can prevail."
In the buoyant mood after Obama entered the White House, Mitchell was seen as a good choice for a president who sought to make Arab-Israeli peacemaking a top and immediate priority.
Stephen Walt, a Harvard professor who is co-author of a 2006 book on the power of the pro-Israel lobby in Washington, emphasized Mitchell's impartiality after the steadfast support president George W. Bush gave Israel.
"Our long-standing policy of one-sided support hasn't been working out so well for the United States, or for Israel," Walt wrote in the Foreign Policy journal website blog. "I think Obama may get this."
In his relentless shuttles to the region, Mitchell sought to coax Palestinians and Israelis back to talks that collapsed after Israel's brief December 2008 invasion of the Gaza Strip to stop Hamas militant rocket fire.
During the long months of behind-the-scenes maneuvers, Mitchell rarely spoke in public and when he did, he kept his cards close to his chest, refusing to discuss the details of negotiations for fear of undermining them.
In September 2010, backed by Obama and Secretary of State Hillary Clinton, he made a breakthrough when Palestinian leader Mahmud Abbas came to Washington for direct peace talks with Israeli Prime Minister Benjamin Netanyahu.
However, the talks collapsed weeks after they started after Netanyahu's right-wing government refused to renew a partial moratorium on West Bank settlements, land where the Palestinians want to build a future state.
US-based analysts criticized the Obama peace team for having made settlements the make-or-break issue by insisting from the outset that Israel halt all settlement construction.
Instead, they said, the administration should have left settlements to the final status negotiations, saying they could have been dealt with under talks over the borders of a future Palestinian state.
This was not Mitchell's first experience with the Middle East.
In 2000 he was charged with presiding the committee bearing his name and finding ways of ending violence between Israelis and Palestinians.
In his report submitted in 2001 he called on both sides to take immediate measures to unconditionally end the violence, but his calls went unheeded.
In Northern Ireland, Mitchell managed to bring together the leaders of the province's two communities with a mixture of compromise and painstaking talks to sign the historic Good Friday agreement in 1998.
At the time Mitchell, a Democrat, was considered one of the only actors in the peace process enjoying the trust of all parties, earning a reputation in Belfast as a safe pair of hands and a shrewd, even-handed operator.
In a book on his experience called "Making Peace" he recounted how local political customs in the province during the talks had tested his efforts as a negotiator.
The youngest of five children, Mitchell was born on August 20, 1933 in Waterville, Maine to a Catholic family of modest means with an Irish father and a Lebanese mother. He was adopted by a Lebanese family after he was orphaned.
After financing his law studies by working part time as a truck driver and a night watchman, he launched into a career as a lawyer, prosecutor and federal judge.
He then entered the US Senate where he sat from 1980 to 1995 for Maine. He led the Democratic majority in the Senate from 1988 to 1994 during the administrations of George H.W Bush and Bill Clinton.
After leaving political life, he became a partner in a cabinet of lawyers and has also served on the board of several large companies.