Mahmoud Abbas, a tough critic of Palestinian violence and an advocate of peace with Israel, agreed today to serve as the Palestinians' first prime minister, a senior adviser to Palestinian leader Yasser Arafat said.

The new position is designed to dilute Arafat's powers and give new impetus to stalled Middle East peace talks.

Abbas, a longtime Arafat associate also known as Abu Mazen, accepted the job after weeks of efforts by international negotiators and Palestinian Authority insiders to win Arafat's consent to a potential major shift in the operations of his government.

Abbas, 68, known for avoiding the media, did not announce the decision. His appointment was confirmed after Abbas met for 90 minutes with Arafat at the Palestinian leader's ravaged compound in the West Bank city of Ramallah.

"Abu Mazen has officially accepted Arafat's appointment to become prime minister," an Arafat spokesman told reporters after the meeting..

Senior Palestinian leaders have sought to prune Arafat's powers for years. But the autocratic representative of the fight for Palestinian statehood only agreed last month to the change. Intense international pressure for Arafat to accept the new post came from the the United Nations, European Union, Russia and the United States as they attempt to restart peace negotiations between Israelis and Palestinians. The United States and Israel have refused to deal directly with Arafat, claiming that he supports terrorism, and have said that new Palestinian leadership was a prerequisite to resuming a cease-fire and peace talks.

Palestinians, Israelis and Western diplomats here generally praised Abbas's appointment, but said it was too early to determine whether he would be granted the power and independence required to rein in Palestinian support for terrorism and curb official corruption. His task is to establish himself as a credible counterweight to Arafat, who retains significant authority as the president of the Palestinian Authority.

A Palestinian Legislative Council session earlier this week debating the prime minister's powers became so heated that the speaker of the parliament was hospitalized for shortness of breath. Abbas expressed strong doubts about the job and had to be convinced that his authority would be accepted before he took it , according to several Palestinian officials who met with him.

"It's going to be difficult, it's going to cause him a lot of anxiety," said Nabil Shaath, a legislator and cabinet member who said he pushed Abbas to take the job. "It's going to cause him a lot of anxiety. The challenge is immense."

So far, the Palestinian legislature has left the description of his job deliberately vague. While some of the prime minister's responsibilities are explicit -- he chooses the cabinet, for instance, and is responsible for the management of the government -- other details are imprecise.

The new prime minister is "responsible for preserving public order and preserving internal security," according to new laws creating his position, but Arafat remains the commander in chief of Palestinian security forces. Arafat also remains the ultimate authority over the Palestinian Authority's foreign affairs.

"The man will have to make himself," said Zalman Shoval, an adviser to the Israeli prime minister, Ariel Sharon. "How far this positive development will go, only the future will tell."

Abbas, who was elected secretary general of the Palestine Liberation Organization in 1996, is known for his strong anti-terror stance. He was one of the architects of the 1993 Oslo peace accords with Israel and over the years has maintained secret access to top Israeli politicians, including Sharon, even as relations between the two sides disintegrated. He has been an outspoken critic of the militarization of the ongoing 30-month-old Israeli-Palestinian conflict, which has claimed nearly 3,000 lives, saying he favors popular resistance, not armed struggle.

Mahmoud Abbas, 68, an advocate of peace with Israel and critic of violence, will become the Palestinian Authority's first prime minister. The move is designed as an effort to dilute the powers of Palestinian leader Yasser Arafat and to help restart the stalled peace talks.