ISLAMABAD, Pakistan — Pakistani and American officials said Sunday that they were increasingly convinced that the leader of the Pakistani Taliban, Hakimullah Mehsud, Pakistan’s chief domestic enemy and the man behind the suicide attack on a C.I.A. base in Afghanistan in December, had died from wounds sustained in a drone strike.

The Pakistani military, which mounted a major offensive against Mr. Mehsud and his loyalists in South Waziristan last fall, said it could not confirm the report. But state-run television set off a storm of speculation on Sunday when it reported that Mr. Mehsud had died.

Government officials in the capital, Islamabad, and Peshawar, the capital of the North-West Frontier Province, said they believed that there was a good chance Mr. Mehsud was dead, though they could not offer proof.

An Obama administration official in Washington said intelligence reports over the weekend came close to a definitive conclusion — about 90 percent certainty — that Mr. Mehsud had died from wounds suffered in a drone strike on Jan. 14 and that he was believed to have been buried in a tribal plot in Pakistan’s tribal areas.

The United States has been eager to retaliate against Mr. Mehsud after he claimed responsibility for the suicide bombing of a C.I.A. base in southeast Afghanistan in late December that killed five agency officers and two private contractors, the deadliest assault against the spy agency in more than 20 years.

American officials said they hoped the death of Mr. Mehsud would signal their resolve against the Taliban groups and their Qaeda allies who have used Pakistan’s tribal areas to strike at American and NATO forces in Afghanistan.

It would be a serious blow, they said, coming at a time when the group has been battered by an escalation in American drone strikes and the offensive by the Pakistani military that has disrupted their operations.

It would not necessarily be a decisive one, however, or one certain to slow the blistering insurgency that the Pakistani Taliban have waged against the Pakistani state with the backing of Al Qaeda.

When Baitullah Mehsud, Hakimullah Mehsud’s predecessor, was killed in a drone attack last August, the Pakistani Taliban were briefly roiled by a succession struggle. But the group resumed its suicide bombings, initiating even more sophisticated and numerous attacks that killed more than 500 Pakistanis since October.

The death of Hakimullah Mehsud, if true, would probably set off a new power struggle. But the organizational setback could be short-lived, as the two men in line to take over from him — Wali ur-Rehman, known as the chief military strategist, and Qari Hussain, the chief instructor on suicide bombers — are considered tough operators.

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