Fallout from the killing of 24 Pakistani soldiers by NATO forces in a friendly fire incident along the Pakistan-Afghanistan border shows few signs of abatement.

Pakistan on Tuesday withdrew soldiers from two of three border posts that are supposed to coordinate with NATO forces operating along the frontier in the ongoing battle against the Taliban and allied Haqqani network, which use tribal areas within Pakistan as bases and safe havens.

U.S. forces were reportedly packing up equipment and preparing to leave an airbase in Pakistan's Baluchistan province, from which U.S. unmanned aerial vehicles performed aerial surveillance and reconnaissance along the border.

And Pakistan boycotted an international conference on Afghanistan's future that opened Monday in Germany.

U.S. officials and analysts say relations between Washington and Islamabad are at their lowest ebb but it is a situation that isn't a surprise.

Pakistan was an early supporter of the Islamist Taliban, who were toppled from power in Afghanistan as a result of U.S. military action in the aftermath of the Sept. 11, 2001, attacks on the United States by al-Qaida, which had training bases in Afghanistan.

Although Pakistan became a partner of the United States and NATO in the war against terrorism -- and a supporter of the new Afghan government of Hamid Karzai -- it has long been suspected of maintaining links to the Afghan Taliban to retain influence if it should return to power in the future.

Those suspicions, fueled by intelligence that Pakistan's intelligence service and military may have passed information to the Taliban about impending NATO attacks in the ongoing insurgency, led to the United States to deliberately not inform Islamabad beforehand of its raid in May on the Pakistani hideout of al-Qaida leader Osama bin Laden.

The result was outrage in Pakistan, where anti-American sentiment runs high. Islamabad accused Washington of violating its sovereignty and demonstrations erupted throughout the country.

When U.S. Navy Adm. Mike Mullen, the outgoing chairman of the U.S. Joint Chiefs of Staff, accused Pakistan's Inter-Services Intelligence -- the country's intelligence agency -- of colluding with a Taliban-connected terrorist group attacking U.S. and NATO forces, backroom mutterings gave way to public pronouncements, charges and countercharges, with U.S. lawmakers calling for a serious review of U.S.-Pakistan relations and the billions of dollars in aid Washington sends Islamabad.

The November friendly fire incident stirred the smoldering fire of resentment.

Reports said the Pakistani soldiers at the border outpost were killed in the early hours of Nov. 26 in a NATO airstrike to support Afghan and NATO troops conducting a joint operation along the border. NATO said the strike was requested by the troops after they were fired upon from the Pakistani side of the border.

Pakistan dismissed the explanation and branded the attack a deliberate act of aggression. It ordered U.S. troops to leave the Shamsi airbase by Dec. 11 and then closed two key border crossings to NATO convoys that transport 40-50 percent of non-lethal supplies from Pakistani ports to NATO troops in Afghanistan.

The crossings are still closed, which means the alliance will have either fly the supplies into Afghanistan, as it does ammunition, or boost the tonnage of non-lethal supplies being sent through Russia and Central Asia.

The closing of Shamsi airbase isn't believed to be a critical dent in NATO's war effort since drones are flown from Kandahar Air Base in Afghanistan, but it will add flying time to reach some areas.

Pakistan's withdrawal of troops who are supposed to coordinate with NATO forces increases the likelihood of friendly fire incidents.

The United States and NATO both expressed regret over the bombing and investigations into the incident have been launched. The probes aren't complete but finger-pointing about apparent miscommunications in the chain of events leading up to the airstrikes continues. This is likely to continue since Pakistan has spurned an offer of a joint investigation.

Both sides, however, recognize the importance of Pakistan in the war on terror, in the war in Afghanistan and in an Afghanistan after the United States and NATO withdraw from the country.

"Registering loud and quick protest against the NATO strike was the right move but at this point some reciprocity would be the constructive way forward," said an editorial in Pakistan's Dawn newspaper. "Pakistan may have refused to formally join the investigation but it should at least cooperate to the full extent it can.

"The next year … is going to be qualitatively different for U.S.-Pakistan ties than the last three years have been. Both administrations will have to strike a delicate balance between being sufficiently nationalist for domestic audiences and cooperative and sympathetic enough to save whatever alliance remains."

That is a reasoned sentiment but how it plays out is another matter.

"This is a fog of war situation. Investigation is going on," U.S. Sen. John McCain, R-Ariz., said on CNN's "State of the Union" program.

"But also the fact is that the ISI, the intelligence arm of the Pakistani army, is still supporting the Haqqani network which is killing Americans. That is unacceptable. So I would gauge our aid, particularly military aid ... directly related to the degree of cooperation they show us," he said.

Pakistan's Parliament isn't quiet on the matter either. It has announced it is reviewing the country's agreements and treaties with the United States and NATO.