Washington (CNN) -- Former U.S. Sen. George Mitchell is resigning as the Obama administration's Mideast envoy, the White House announced Friday.
Mitchell has served as President Barack Obama's point man in the region as the administration has tried to keep Arab-Israeli peace talks on track.
Deputy Middle East Envoy David Hale will take Mitchell's place, according to the White House.
"George Mitchell has worked as a tireless advocate for peace as the U.S. special envoy for the Middle East," President Barack Obama said in a written statement. He "leaves behind a proud legacy of dedicated public service and the country owes him a debt of gratitude for his extraordinary commitment."
Mitchell's resignation, which takes effect May 20, comes at a pivotal moment in the Arab world. Obama is scheduled to deliver an address Thursday on the "Arab Spring": the uprisings that have shaken long-standing autocratic regimes across North Africa and the broader Middle East.
In addition, Israeli Prime Minister Benjamin Netanyahu and Jordan's King Abdullah are scheduled to visit Obama next week. Netanyahu will also deliver an address to Congress.
Mitchell, a Democrat from Maine, was among the president's first appointments. He was named Mideast envoy on January 22, 2009, two days after Obama took office.
Among other things, he played a key role in Clinton-era negotiations regarding the status of Northern Ireland that resulted in the Good Friday Peace Agreement.
Mitchell has repeatedly reaffirmed the importance of a comprehensive peace in the Middle East, including Israeli-Palestinian agreement on a two-state solution and normalization of relations between Israel and both Syria and Lebanon.
New questions about the viability of the stalled peace process were raised this month in the wake of a formal reconciliation agreement between the two largest Palestinian factions: President Mahmoud Abbas' party, the West Bank-based Fatah, and the Islamist group Hamas, which rules Gaza.
Both Israel and the United States consider Hamas a terrorist organization and have voiced strong opposition to the inclusion of the group in any unity government, demanding that it first renounce violence, recognize the state of Israel and abide by all previous agreements.
Netanyahu has called on the Palestinian Authority to pull out of the deal, saying it jeopardizes prospects for a peace agreement.
A senior Israeli government official recently said the government views Hamas' involvement as a "fundamental impasse."
The agreement between Hamas, Fatah and smaller Palestinian factions calls for the establishment of a new Palestinian caretaker government and for parliamentary and presidential elections next year.
CNN's Ed Henry and Alan Silverleib contributed to this report.