..top leaders of Al Qaeda.
Washington - The President hesitates to give full support to clandestine CIA search-and-destroy program, which launches missile strikes from remotely piloted drone aircraft, has killed more than a dozen senior leaders of Al Qaeda during the last two years.

Among the dead: Abu Khabab al-Masri, reputed to be Al Qaeda's top expert on weapons of mass destruction, and Baitullah Mehsud, leader of the Pakistani Taliban and reputed mastermind of the murder of Benazir Bhutto.

U.S. government spokesmen won't even confirm the program's existence, but a U.S. national-security official—who, like others cited in this article, declined to be named talking about sensitive information—says the program has been so successful that some counterterrorism officials want to expand it.

They say the drones have been effective not just in killing terrorists but also in keeping them on the run and disrupting their ability to plan new attacks. They have asked for authority to target terrorists in more densely populated areas of Pakistan.

One person stands in the way of expanded missile strikes: President Obama.
Five administration officials tell NEWSWEEK that the president has sided with political and diplomatic advisers who argue that widening the scope of the drone attacks would be risky and unwise. Obama is concerned that firing missiles into urban areas like Quetta, where intelligence reports suggest that Taliban leader Mullah Mohammed Omar and other high-level militants have sometimes taken shelter, would greatly increase the risk of civilian casualties. It would also draw protests from Pakistani politicians and military leaders, who have been largely quiet about the drone attacks as long as they've been confined to the country's out-of-sight border region. The White House has been encouraged by Pakistan's own recent military efforts to root out militants along the Afghan border, and it does not want to jeopardize that cooperation.

The internal debate about the drone program has been going on for nearly a year. A former senior intelligence official says that, within days of his inauguration, Obama and his top aides began discussing expanding the operation from a relatively limited area along the AfPak border to a broader range of targets like the Pakistani regions of Baluchistan and South Waziristan. Obama has not closed the door on wider drone attacks. One of the officials notes that the administration is likely to continue to debate, and even plan for the possibility of expanding, drone operations in the future—if only to keep the pressure on Pakistan to maintain its current efforts to capture and kill terrorists. A White House spokesperson had no comment.