WASHINGTON: U.S. counterterrorism officials believe Pakistani Taliban leader Hakimullah Mehsud is dead following a missile attack last month, a senior intelligence official said Wednesday in the strongest signal that Washington has offered about the militant's fate.

Neither Pakistan nor the U.S. has officially confirmed the death of Mehsud, who commands an al-Qaida-allied movement that is blamed for scores of suicide bombings and is suspected in a deadly attack on a CIA base in Afghanistan late last year.

Mehsud's death would be the latest successful strike against suspected terrorists by the U.S. and its allies. The U.S. has recently stepped up attacks from unmanned aircraft in Pakistan, and a closer collaboration with Yemen has led to recent airstrikes there. President Barack Obama highlighted the increasing success of such attacks in his State of the Union address last week.

The U.S. intelligence official, speaking on condition of anonymity to discuss sensitive security matters, said the conclusion that Mehsud is dead represents the best collective information of U.S. intelligence agencies. Since the attack, authorities have said they were growing increasingly confident Mehsud was dead. The official would not say what evidence the U.S. had gathered.

The statement came after days of posturing by Pakistani Taliban officials, who first said they would prove their leader was alive and well, then reversed course and said they saw no need to prove it.

The attack by a U.S. drone came after Mehsud appeared in a video alongside the Jordanian suicide bomber who killed seven CIA employees at a remote base in Afghanistan. The bomber, Humam Khalil Abu-Mulal al-Balawi, said he carried out the attack in retribution for the death of former Pakistani Taliban leader Baitullah Mehsud in a U.S. drone strike last August.

Baitullah Mehsud's death gave leadership of the Pakistani Taliban to his deputy, Hakimullah Mehsud, a 28-year-old with a reputation as a particularly ruthless militant.

He has taken responsibility for a wave of brazen strikes inside Pakistan, including the bombing of the Pearl Continental hotel in the northwestern city of Peshawar last June and the attack on the Sri Lankan cricket team in Lahore earlier that year. There is a $590,000 bounty on his head.

U.S. drones are piloted remotely and can be controlled from local bases or from the United States. Though the program is officially a secret, the attacks are well publicized. They are Washington's only known military response to al-Qaida and Taliban militants along Pakistan's border with Afghanistan.