The defense officials said the principal Pakistani aim in isolating and eventually striking against insurgents inside Waziristan, a tribally governed region on the Afghanistan border, would be to neutralize the threat posed by Baitullah Mehsud, the Taliban warlord who U.S. officials believe was behind the assassination in 2007 of former Pakistani prime minister Benazir Bhutto.

That aim overlaps but does not precisely coincide with Washington’s desire for Pakistani forces to gain sufficient control of the rugged terrain in Waziristan to deny its use as a haven by al-Qaeda fighters and leaders, apparently including Osama bin Laden. “There are some groups we’d like Pakistan to take more action against,” a senior defense official said in a separate briefing for reporters yesterday.