Former Senator George Mitchell submitted his resignation Friday from his role as U.S. Special Envoy for Middle East Peace, saying in his resignation letter that he strongly supports President Barak Obama's vision for peace.

"I strongly support your vision of comprehensive peace in the Middle East and thank you for giving me the opportunity to be part of your administration," said Mitchell in his resignation letter. "It has been an honor for me to again serve our country."

Mitchell is leaving as peace talks between Israel and the Palestinians have come to a standstill, though he did not mention the matter in his resignation. He said that when he took on the role his intention was to serve for two years and more than that has now passed.

His resignation will be effective May 20 - the same day Prime Minister Benjamin Netanyahu visits the White House.

After accepting Mitchell's resignation, Obama said in a statement Friday that the United States owes him a debt of gratitude. "Mitchell has worked as a tireless advocate for peace," said the President. "His deep commitment to resolving conflict and advancing democracy has contributed immeasurably to the goal of two states living side by side in peace and security."

Obama described Mitchell as one of the finest public servants the United States has ever had. "Even though he already had an extraordinary legacy - serving the people of Maine, leading the Senate, and bringing peace to Northern Ireland – he took on the toughest job imaginable and worked grueling hours to advance the interests of the United States and the cause of peace," he said.

The President named Mitchell's deputy, David Hale, as his replacement for the time being. "I have every confidence in David's ability to continue to make progress in this important effort," Obama said in the statement.

An administration official, speaking on condition of anonymity, said earlier that Mitchell's staff is expected to remain in place at least temporarily.

Mitchell's departure comes ahead of U.S. President Barack Obama's expected speech laying out his new Middle East policy.

Mitchell, 77, a former U.S. senator who helped broker the Northern Ireland peace deal, was one of the first members of Obama's foreign policy team to be announced, on Obama's second full day in office in January 2009, and has shuttled extensively between Washington and Middle East capitals trying to set up new negotiations.

Direct peace talks resumed briefly last year but broke down over a dispute surrounding Jewish settlement construction in the West Bank. Faced with a deadlock, the United States in December scrapped efforts to re-launch direct peace talks and Mitchell has not visited the region since then. Hale has made the trips between Washington, Ramallah and Jerusalem instead, as has Obama's senior adviser on the Middle East, Dennis Ross.

In response to Mitchell's resignation, the American pro-Israel lobby group issued a statement saying they appreciate Mitchell's efforts to set up negotiations and "deeply regret Palestinian Authority President Mahmoud Abbas’ continued unwillingness to negotiate directly with his Israeli counterpart without preconditions."

The lobby group added that Mitchell made it clear to both parties that the only way to "true peace" was via direct, bilateral negotiations, but said that instead of making peace with Israel, Abbas opted for reconciling with Hamas, "a U.S.-designated terrorist organization responsible for the death of countless civilians and unwilling to recognize the existence of the Jewish state."

The Israeli Ambassador to the United States Michael Oren said Israel appreciates the effort and contributions Mitchell made to mediate the end of conflict between Israel and the Palestinians, adding that Israel remains committed to the vision Mitchell "so tirelessly pursued."