WASHINGTON—The U.S. is pushing to expand a secret CIA effort to help Pakistan target militants in their havens near the Afghan border, according to senior officials, as the White House seeks new ways to prod Islamabad into more aggressive action against groups allied with Al Qaeda.

The push comes as relations between Washington and Islamabad have soured over U.S. impatience with the slow pace of Pakistani strikes against militants who routinely attack U.S.-led troops in Afghanistan. President Obama has said he will begin to withdraw troops from Afghanistan in July, increasing the urgency to show progress in the nine-year war against the Taliban.

The U.S. asked Pakistan in recent weeks to allow additional Central Intelligence Agency officers and special operations military trainers to enter the country as part of Washington's efforts to intensify pressure on militants.

The requests have so far been rebuffed by Islamabad, which remains extremely wary of allowing a larger U.S. ground presence in Pakistan, illustrating the precarious nature of relations between Washington and its wartime ally.

The number of CIA personnel in Pakistan has grown substantially in recent years. The exact number is highly classified. The push for more forces reflects, in part, the increased need for intelligence to support the CIA drone program that has killed hundreds of militants with missile strikes. The additional officers could help Pakistani forces reach targets drones can't.

There are currently about 900 U.S. military personnel in Pakistan, 600 of which are providing flood relief and 150 of which are assigned to the training mission.

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