RAMALLAH, West Bank ? Palestinian legislators Monday began wresting power away from their leader, Yasser Arafat, and giving it to the newly created post of prime minister, in response to pressure from the United States and because of the stalemate in the conflict with Israel.

During a stormy session that went into the night, members of the Palestinian Legislative Council first approved the position of prime minister, some hailing the moment as nothing short of revolutionary, and then defined the position’s powers.

Instead of relegating Arafat to a ceremonial role, as was urged by the United States and Israel, the legislators left significant powers in his hands, including the authority to conduct negotiations with Israel and oversight of Palestinian security forces.

Arafat, an enduring symbol of Palestinian nationalism known for his survival skills, had agreed only reluctantly to appoint a prime minister, and he must now approve the bill for it to become law.

His nominee, Mahmoud Abbas, also known as Abu Mazen, would then have three weeks to form a new government, but officials said that task could be completed much sooner.

Palestinian officials said that Abbas, as secretary general of the Palestine Liberation Organization, would have a significant role in peace talks but that the final say in any decisions ultimately belongs to Arafat.

Abbas, 67, is an outspoken critic of the armed uprising against Israel and was the architect of an interim peace accord that established the Palestinian Authority. He has met with top Israeli leaders even after they cut off contacts with Arafat.

U.S. Ambassador to Israel Daniel Kurtzer indicated before the legislature voted that U.S. officials, who have shunned Arafat, expect the new prime minister to be actively involved in any future negotiations.

“He should be empowered and willing to help move the Palestinians from violence to peace,” Kurtzer said after meeting with Israeli Foreign Minister Silvan Shalom. “This would be a very welcome step, in our view.”

Israeli officials, who have labeled Arafat an “obstacle to peace” and declared him irrelevant, remained cautious. Shalom said creation of the prime minister’s post was positive but said the central issues are the “powers that will be granted.”