WASHINGTON: The CIA's targeted killing program in Pakistan, once the mainstay of President Barack Obama's counterterrorism effort, is winding down.

Because of stricter rules, diplomatic sensitivities and the changing nature of the al Qaeda threat, there hasn't been a US drone strike in Pakistan's tribal areas since Christmas. And American officials say opportunities for drone attacks will dwindle further as the CIA and the military draw down in neighboring Afghanistan, reducing their intelligence-gathering footprint.

“The program (in Pakistan) appears to have ended,” said Peter Bergen, who has closely studied drone strikes for the New America Foundation, a Washington think tank.

US officials won't go that far, but Obama announced this week a plan to pull nearly all American troops out of Afghanistan by the end of 2016.

The targeted killing program in Pakistan relies on drones flown from, and intelligence gathered in, US bases in Afghanistan that would then be closed.

Also read: Obama stresses need for transparency in strikes

In a major foreign policy speech at the US Military Academy Wednesday, Obama said the US would continue to carry out occasional drone strikes against terrorist targets, but he cited Yemen and Somalia, not Pakistan, where Hellfire missiles once rained down at a rate of two per week.

Armed US drones are still flying over Pakistan's tribal areas, and CIA targeting officers are still nominating militants to the kill list, according to US officials who spoke on condition of anonymity because they weren't authorised to discuss the covert program publicly. But over the last five months, no missiles have been fired.

Several factors are driving the change, US officials say. Many of the senior al Qaeda figures in Pakistan have been killed. Those who remain are much harder to target because they are avoiding mobile phones and traveling with children, benefiting from stricter targeting rules designed to prevent civilian casualties.

The drawdown of US troops from Afghanistan has eliminated the need for “force protection” strikes against large gatherings of militants in Pakistan suspected of plotting attacks against American troops.

Also, the tribal areas of Pakistan are no longer the hotbed of al Qaeda activity they once were. Hard core militants from Pakistan have gone to Syria and Yemen, home to al Qaeda in the Arabian Peninsula, which US officials consider the most dangerous al Qaeda affiliate.

And Obama administration officials are pushing to have the US military, not the CIA, carry out drone strikes. Since the military generally requires permission from a country to operate on its territory, most analysts don't believe it could carry out regular drone attacks in Pakistan.

The CIA and the White House declined to comment.

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The current drone ceasefire in Pakistan is by far the longest pause since President George W. Bush ordered a stepped-up campaign of targeted strikes in that country's tribal area in the summer of 2008.

The pace intensified under Obama. All told, there have been 354 strikes in Pakistan since 2004, according to Long War Journal, a website that tracks the strikes through media reports.

But the rate of strikes began falling in 2011 and decreased each year since. Last year, Obama announced stricter targeting criteria, including a provision that no strike would occur unless there was “a near certainty” that civilians would not be harmed.

Even before that, American officials appear to have made the calculation that it was no longer worth attacking lower level militants in Pakistan, given the bitter opposition to the strikes in that country.

Two studies, one by the New America Foundation and one by researchers at NYU and Stanford, estimate that as few as 2 per cent of those killed in Pakistan drone strikes since 2004 have been senior militants.

Most killed were lower level fighters, and some fraction — how large is disputed — have been civilians.

Obama seemed to allude to the backlash Wednesday when he said, “Our actions should meet a simple test: we must not create more enemies than we take off the battlefield.”

In December, the Obama administration reached an informal deal with Pakistan that the CIA would suspend drone strikes – except against the most senior al Qaeda leaders – while the government of Prime Minister Nawaz Sharif pursues peace talks with the Taliban.

The talks have sputtered, and last week, Pakistani fighter jets killed more than 60 people in North Waziristan, a militant stronghold, according to local media reports.

But Pakistani officials say the cessation in drone strikes has strengthened support for counterterrorism operations among a public that deeply resented an American bombing campaign on its soil.

The hiatus has made the government feel that the US is hearing Pakistan's concerns, said one senior official, speaking only on condition of anonymity because he was not authorised to comment by name.