Administration, military and intelligence officials told the New York Times if U.S. President Barack Obama decides to withdraw all American troops from Afghanistan by the end of this year, it could mean the loss of bases for drone strikes against remnants of al-Qaida in neighboring Pakistan.
It would also negatively impact U.S. ability to respond to any nuclear crisis in the region.
Thus far, the Afghan government of President Hamid Karzai has refused to sign the Bilateral Security Agreement, which the Obama administration says is needed to decide how many residual U.S. troops will be kept in the country after the U.S.-led NATO forces complete their withdrawal by the end of this year. Without the agreement, Obama may be forced to pull out all U.S. troops.
The U.S. officials speaking to the Times said the concern also relates to how troop levels in Afghanistan directly affect long-term American security interests in Pakistan.
The Times said the Obama administration has set up a team of intelligence, military and policy specialists to come up with alternatives if the security agreement is not signed.
If all U.S. troops are withdrawn, the officials said the Central Intelligence Agency's drone bases in Afghanistan would need to be shut down for security reasons. The concern is any alternative sites may be too far away for the drones to reach the mountainous regions in Pakistan where al-Qaida's central command is believed to be hiding.
The officials said any distant bases also would make it difficult to respond speedily to any nuclear crisis in Pakistan or India.
However, a senior official told the Times the administration is determined to come up with alternatives if needed.
"Karzai has believed for some time that he has this leverage -- that we need him and his bases more than he needs us," former State Department official Daniel Markey told the Times.
The report said the Reapers, the newest and most capable of the unmanned armed vehicles, have a range of up to 1,100 miles, which would put Pakistan's tribal areas within range of some bases such as in Kyrgyzstan.