Shortly before the United States ended a two-month pause in missile strikes on militants in Pakistan last month, senior U.S. officials telephoned their Pakistani counterparts and told them Washington would be resuming its covert drone program despite mounting objections in Islamabad.Vice President Joe Biden and Secretary of State Hillary Clinton were among those who spoke with Pakistani officials shortly before the eight-week pause in the drone program ended, sources familiar with the issue said.General Martin Dempsey, chairman of the U.S. Joint Chiefs of Staff, spoke to his Pakistani counterpart General Ashfaq Kayani around the same time, the sources said, but a U.S. defense official said the two men did not discuss drone strikes.The strike that followed on January 10, when U.S. aircraft fired missiles at a home in the North Waziristan tribal area, was the first such attack since U.S. aircraft, in a mishap that plunged bilateral ties into a tailspin, killed 24 Pakistani soldiers along remote border with Afghanistan.The November 26 border incident infuriated a vulnerable government in Islamabad and prompted Pakistani officials to signal, in more emphatic terms than they had previously, that they would no longer accept U.S. drone strikes. That set the Obama administration up for yet another potential collision with Pakistan as it continues a controversial drone program that has become a centerpiece of U.S. efforts to quash militancy there.The Pakistani border deaths, which NATO deemed an accident and a tragedy, prompted Pakistan to shut down an overland supply route that is key for NATO troops in Afghanistan and to force U.S. personnel off an air base in southwest Pakistan that had been used to launch drone strikes in Pakistan's tribal areas.In public, the U.S. missile strikes are a frequent target of criticism for Pakistani politicians, who decry them as a violation of the country's sovereignty. But in private, Pakistani leaders have long supported and even encouraged the strikes provided they steer clear of certain areas and targets.Yet even as both governments try to put the relationship back together, current and former U.S. officials speaking on condition of anonymity said the Obama administration will not hesitate to continue the aerial strikes when targets and intelligence are sufficiently compelling.But the U.S. officials also said they are unlikely to give Pakistan advance notice about drone strikes for the time being, given the lack of trust on both sides and what American officials describe as a track record in Pakistan of intelligence leaks allowing militants to get away before planned attacks are launched.However, drone operators might still use information from Pakistan's intelligence agency ISI to locate targets.The strikes have become central to President Barack Obama's counter-terrorism strategy in Pakistan, where the United States has failed to persuade Islamabad to take stronger action against militants that have long stoked violence in Afghanistan.Many U.S. officials complain that messages from Pakistan's top leadership have been - and continue to be - inconsistent.There was no immediate comment from the White House or the State Department on the resumption of the strikes.The strikes may take on additional importance as the United States rushes to make military progress ahead of a looming deadline to withdraw most of its troops from Afghanistan.Yet the drone program has also fueled simmering anti-American sentiment in Pakistan, heaping additional pressure on the weak civilian government and even on its powerful military, already buffeted by unusual public criticism after the unilateral U.S. raid that killed al Qaeda leader Osama bin Laden in Pakistan last year.Following the November border incident, U.S. officials insisted there was no formal decision to suspend drone strikes.Other strikes have followed the initial January 10 attack, including several reported to have killed senior militants including some reportedly affiliated with al Qaeda or the Pakistani Taliban.But U.S. officials acknowledged that the strikes are likely to proceed at a lower rate in the immediate future, in part because of bilateral tensions and in part because launching the flights from neighboring Afghanistan has posed logistical and operational obstacles.While officials in Islamabad have signaled they are ready to repair ties to a certain extent, the drone strikes will be a major consideration as Pakistani lawmakers conclude a parliamentary review of ties with the United States.Sherry Rehman, the former information minister and human rights campaigner who last month became Islamabad's new ambassador to the United States, suggested in her first address in Washington that the review and the low point following the border deaths offered a chance to improve U.S.-Pakistani cooperation."Critics of a strong US-Pakistan relationship are questioning its viability in both nations, yet I feel we can use this opportunity to re-set our relationship on a clearer, more stable footing," she said last week during a speech at the U.S. Institute of Peace.Foreign Minister Hina Rabbani Khar, who will meet Clinton in London on Thursday to try to repair damaged ties, said parliament was looking at "terms of re-engagement."Rehman said better communication and more consistent messages from public officials was needed on both sides.