The Pakistani army is bolstering air defenses along its Afghan border, including deploying shoulder-to-air missiles, officials said this week — a move that could threaten NATO aircraft and reflects the depths of anger and suspicion here after a deadly NATO airstrike.

Underlining how just raw the wounds still are within the Pakistani army, the head of military operations, Maj. Gen. Ashfaq Nadeem, told a Pakistani Senate committee Thursday that the strike in November that killed 24 soldiers was “a pre-planned conspiracy” and warned that Pakistan could expect more such attacks “from our supposed allies,” local newspapers reported.

It is a view widely shared within the military and among the general public here — that the United States carried out the attack to punish Pakistan for allowing Islamist militants to use its territory to launch attacks in Afghanistan.

The United States has expressed condolences to Pakistan for the “regrettable incident” but says it will not respond to demands for an apology until the Pentagon completes an investigation. The probe’s findings are not due to be released until Dec. 23.

Pakistan responded to the attack by closing U.S. and coalition military supply routes to Afghanistan and also boycotted an international conference in Germany on the future of Afghanistan.

But the latest move, potentially threatening NATO jets in the border region, underlines the depth of distrust in a relationship that many observers here say is now irreparably damaged, despite billions of dollars of U.S. aid to Pakistan over the past decade.

“Primarily it will be early warning systems, but there will be certain weapons deployed in certain areas,” deputy military spokesman Brig. Gen. Azmat Ali said Friday, stressing that the move was defensive rather than offensive in nature.

“It became very embarrassing for our troops. They were killed like sitting ducks,” he said, adding that the decision had been taken in response to pressure from the troops themselves. “If there is another attack, they should have something to defend themselves.”

Military officers said there were already some short-range anti-aircraft guns in the border region, but more had been deployed since May 2, when U.S. helicopters flew into Pakistan unnoticed to carry out a raid to kill Osama bin Laden.

Radar systems have also been upgraded since the Nov. 26 NATO airstrike, and shoulder-to-air missiles have been deployed in the border region along with small contingents of troops trained in their use, a military official said.

The rules of engagement have also changed: After the airstrike, army chief Ashfaq Pervez Kayani told commanders along the border they could return fire without awaiting permission from central command, as had been the case in the past.

“The field commanders have been provided with surface-to-air missiles that can be fired from the shoulder,” said a senior military official in Peshawar who spoke on the condition of anonymity because he was not authorized to speak to reporters. “The missile system is run by a small team of three to four military people who are trained in firing the missiles.”

U.S. officials say the November airstrike occurred when a joint U.S. and Afghan patrol requested air support after coming under fire. They say they checked with the Pakistani military first to see whether Pakistani troops were in the area.

But Pakistan says the Americans gave the wrong coordinates, knew the location of the Pakistani base that was attacked and continued attacking for a considerable length of time even after the Pakistanis asked them to stop.

Javed Ashraf Qazi, head of the Pakistani Senate defense committee, said his panel supports the military’s plan to bolster air defenses but added that any deployment would be selective.

“You cannot deploy these systems on each and every outpost. Sometimes these posts are attacked by militants, and you may lose these weapons,” Qazi, a retired army general and former head of Pakistan’s powerful Inter-Services Intelligence agency, told the Associated Press.

The relationship between the United States and Pakistan suffered a blow in January, when a CIA contractor shot two Pakistanis to death on the streets of Lahore. It was damaged again by the bin Laden operation in May. Underlining the depth of ill-feeling, then-Chairman of the Joint Chiefs of Staff Adm. Mike Mullen accused Pakistan’s spy agency of supporting a deadly attack on the U.S. Embassy in Kabul in September.

But the latest incident has sent relations into such a spiral that many observers wonder whether they can be rescued.

“It is almost like a point of no return,” said columnist and military expert Ayesha Siddiqa. “There is little left in the relationship.”

Pakistan’s military has been demanding a much smaller CIA footprint in the country and more information on what U.S. intelligence agents are doing here; more control over and information on drone strikes; and a greater role for Pakistan in Afghan reconciliation efforts. But those steps would require a certain level of trust, which at this point is conspicuously missing.

Observers here are skeptical about the chances of the two sides ever really patching up their differences, with future cooperation likely to be more limited and more covert. They say the two countries no longer share the same strategic goals in the region.

“This used to be the most pro-American army in Asia, but it is mind-boggling how things have turned around in the last 10 years,” said defense analyst and former helicopter pilot Ikram Sehgal. “In fact, the relationship has broken down.”

Special correspondents Shaiq Hussain in Islamabad and Haq Nawaz Khan in Peshawar contributed to this report.