ISLAMABAD, Pakistan (AP) - NATO airstrikes that killed 24 Pakistani soldiers came just as the difficult relationship between the U.S. and Pakistani militaries was showing signs of improvement.
Only hours earlier, U.S. Marine Gen. John Allen, the coalition's top commander in Afghanistan, and Pakistan's army Chief Gen. Ashfaq Pervez Kayani concluded a meeting that sought to find common ground, a senior U.S. official told The Associated Press.
The official said the two men discussed areas of cooperation and "basically what we could do for each other."
Now, Kayani is under renewed pressure from his rank and file, intelligence sharing has stopped and Pakistan has withdrawn its offer to nudge the Afghan Taliban to the negotiation table.
On its website, the U.S. Embassy warned of possible retaliation against Americans and said some U.S. government personnel outside Islamabad were being recalled to the capital as a precaution.
The White House said Monday that President Barack Obama considers the incident a tragedy and that the administration is determined to look into the circumstances of the airstrikes.
White House spokesman Jay Carney said the president extends sympathy to the families of the dead soldiers and to Pakistan. Carney said: "We take it very seriously."
A complete breakdown in the U.S.-Pakistani relationship seems unlikely, and both sides know that more is at stake than ever before.
Nevertheless, the senior U.S. official said the weekend pre-dawn raids have left the relationship "the worst it has been" - dashing hopes of restoring ties damaged by Pakistani anger over the unilateral U.S. raid on Osama bin Laden's hide-out, and U.S. outrage that the al-Qaida leader was living not far from Pakistan's version of West Point.
Saturday's airstrikes lasted almost two hours and persisted even after Pakistani commanders pleaded with coalition forces to stop, the Pakistani army claimed Monday.
NATO described the incident as "tragic and unintended" and promised a full investigation.
Afghan officials, speaking on condition of anonymity because of the ongoing investigation, said Afghan commandos and U.S. special forces were conducting a mission on the Afghan side of the border and received incoming fire from the direction of the Pakistani posts. They responded with airstrikes.
Pakistan denies it fired first at NATO.
The poorly defined, mountainous border has been a constant source of tension between Pakistan and the United States.
NATO officials have complained that insurgents fire across the frontier into Afghanistan, often from positions close to Pakistani soldiers who have been accused of tolerating or supporting the militants.