Palestinian President Mahmoud Abbas on Thursday designated Prime Minister Ismail Haniyeh of Hamas to form a new government after accepting his resignation. This paves the way for installation of a unity government with the Islamic Hamas and Abbas' more moderate Fatah.

Haniyeh has five weeks to form the government along the lines of an agreement hammered out last week at a summit in Mecca, Saudi Arabia.

Meanwhile, aides to Abbas said the United States has informed him that it will shun any members of a future Hamas-Fatah coalition.

That position would be a severe blow to Abbas, a Fatah moderate who is trying to reach a power-sharing deal with the radical Hamas group to end Palestinian infighting and to get crippling international sanctions on the government lifted.

Until now, Washington had withheld judgment on the power-sharing deal.

Abbas received word of the new U.S. position in a phone call from U.S. Assistant Secretary of State David Welch late Wednesday, the aides said, speaking on condition of anonymity because they were not authorized to discuss the issue. Jacob Walles, the U.S. consul general in Jerusalem, then delivered the same message to Abbas in person Thursday, the aides said.

The U.S. Consulate in Jerusalem had no immediate comment.

While the U.S. government would not deal with the coalition government, it would still maintain ties with Abbas and his office, his aides said.

Palestinian negotiator Saeb Erekat would only say that U.S. officials have made it clear to the Palestinians that any government must adhere to the principles laid out by the Quartet of Mideast mediators — recognize Israel, renounce violence and back previous peace deals with Israel.

Erekat met with senior U.S. officials in Washington last week to prepare for a three-way Mideast summit in Jerusalem on Monday. He also was involved in the meeting Thursday between Abbas and Walles.

"The Americans reiterated their position that their relations with the government will depend on the government's compliance with the Quartet's principles," he said.

Israeli Prime Minister Ehud Olmert told reporters traveling with him in Turkey that he wanted to maintain ties with Abbas, who is widely known by his nickname, Abu Mazen.

"I am against cutting off ties with Abu Mazen," he said. "Abu Mazen was elected directly and his authority derives from this. I don't see anything to deter a meeting with Abu Mazen. He is committed to the Quartet principles and the road map (peace plan)."

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