Pakistan has withdrawn from an international conference on stabilizing Afghanistan to protest the deadly attack by American forces on its troops, widening a fresh rupture in ties with a nominal ally that is endangering the US plan for gradually ending the war.
In an unusually hostile comment, a top Pakistani army general said on Tuesday that the deaths of 24 Pakistani soldiers were the result of a "deliberate act of aggression." He said the military has not decided whether to take part in an American investigation into the weekend encounter along the mountainous Afghan border.
The hard line was aimed partly at pacifying the country's anti-American public, most of whom detest their leaders' close association with Washington. The uncompromising stance of the army was also likely designed to press for more concessions from Washington.
Regardless of motive, Pakistan's retaliatory moves and tough rhetoric lower the chances of greater cooperation in the Afghan war.
Those ties have been beset by crises for the most of the year, most notably after the US raid on May 2 that killed Osama bin Laden and wounded Pakistani pride.
Pakistan needs American aid and diplomatic support but has shown no willingness to listen to American requests to fight insurgents who use the border as a staging area to carry out attacks inside Afghanistan. Indeed, the army is widely believed to support those militants, hoping they can help ensure that any future regime in Kabul shares Pakistan's hostility to India.
Differing versions of Saturday's incident have emerged, but all agree that 24 Pakistan soldiers were killed in attacks on two bases by NATO aircraft. NATO has described the incident as "tragic and unintended," and US officials have expressed their sympathies with the families of the dead.
Hours after the attack, Pakistan closed its two crossings on the western border to trucks delivering fuel, vehicles and food to NATO troops in Afghanistan. A NATO official said military operations could run at the current pace for "several months" because the alliance has stockpiles of supplies and alternative routes into the country.
Islamabad also ordered the US to vacate within 15 days an air base in southwest Pakistan that housed CIA drones which attack militants along the Afghan border. U.S. officials have said this will not greatly impact the drone program because most of the aircraft are flown from bases in Afghanistan.
The decision to skip the Afghan conference Monday in Bonn, Germany, was made during a Pakistani Cabinet meeting.
German Chancellor Angela Merkel said she hoped the government would reconsider.
"They should still understand that the Afghanistan conference is a very important one. It's a very good opportunity to bring forward the political process," she said.
Pentagon press secretary George Little also urged Pakistan to come.
It was once hoped that the conference would help toward reconciliation with the Taliban, but the assassination in September of former Afghan President Burhanuddin Rabbani severely undermined efforts to reach out to the insurgency.
Few had high expectations the conference would result in significant progress. But the absence of Pakistan, the most important country in the peace process, will make even minor achievements more difficult.
Soon after the Pakistani Cabinet meeting ended, two army generals briefed several dozen Pakistani newspaper editors, talk-show hosts and defense analysts on the fallout from the attack.
Maj. Gen. Ashfaq Nadeem, director general of military operations, called the incident a "deliberate act of aggression" and said it was "next to impossible that NATO" did not know it was attacking Pakistani forces, according to people who attended the briefing, which was closed to non-Pakistani media.
Gen. James Mattis, head of US Central Command, announced on Monday that he had appointed Brig. Gen. Stephen Clark, an Air Force special operations officer, to lead an investigation and include input from the NATO-led forces as well as the Afghan and Pakistani governments.
But Nadeem said the army may not cooperate with the investigation, saying it had little faith that any US probe will get to the bottom of what happened. He said other joint inquiries into at least two other similar, if less deadly, incidents over the last three years had "come to nothing."
Although Pakistan is angry over the deaths of its soldiers, it also appears to realize this is a moment to reset ties with the United States in its favor, analysts said. The incident has given space to right-wing, Islamist voices that have long called for the army and the government to sever ties with America and cut off the supply lines.
Anthony Cordesman, an analyst for the Center for Strategic and International Studies in Washington, said this crisis likely "will get papered over" with some sort of US or NATO apology and a "bribe in the form of better aid flows."
"In the process, however, the US will face even less prospect that Pakistan will really crack down on insurgent groups in the border area, or stop seeing Afghanistan as an area where it competes with India and which is useful for strategic depth in some future war with India," Cordesman said.