Mr. Mehsud, perhaps Pakistan’s most notorious militant, leads an umbrella group of the militants in the border areas, known as the Tehrik-i-Taliban Pakistan, or the Taliban Movement of Pakistan. Pakistan’s previous government and American officials have said a communications intercept linked him to Ms. Bhutto’s assassination, and a Pakistani court has charged Mr. Mehsud in absentia with planning it.

Ms. Bhutto’s widower, Asif Ali Zardari, and other members of her party have cast doubt on the previous government’s version of events, however.

Farhatullah Babar, a spokesman for the party, called the cease-fire announcement by Mr. Mehsud a “welcome development,” but said the negotiations were continuing. “No deal has been finalized,” he said by telephone. Regarding Mr. Mehsud’s alleged involvement in Ms. Bhutto’s assassination, he said the “Pakistan Peoples Party had not named Baitullah Mehsud” as being responsible for her attack.

Even so, Mr. Mehsud claims to have scores of suicide bombers at his disposal, and he is blamed for many if not most of the suicide attacks in Afghanistan and Pakistan over the last two years. Diplomats and Afghan officials said they believed that the new government recognized that he was a long-term danger, even though it may be seeking a short-term reprieve from his attacks through the negotiations.

Previously, leaders of the Awami National Party, which leads the government in North-West Frontier Province and is part of the national coalition, have said they do not think Mr. Mehsud will enter into serious negotiations.

In Washington, Assistant Secretary of State Richard A. Boucher said the United States viewed the negotiations as a tactic, acknowledging that it had been tried before by Mr. Musharraf. The concern was follow-through and enforcement, he said. “The outcome is what matters,” he said. “There has to be less violent activity. There has to be an end to the Al Qaeda elements who are very dangerous, who are up there plotting and planning.”

The draft agreement, which was approved by senior political leaders in Islamabad, has the backing of the military establishment, officials here said.