CIA drone missiles hit militant targets in Pakistan on Sunday for the first time in a month, as the United States ignored the Pakistani government’s insistence that such attacks end as a condition for normalized relations between the two perpetually uneasy allies.

The drone strikes, which have long infuriated the Pakistani public, killed four al-Qaeda-linked fighters in a girls’ school they had taken over in the North Waziristan tribal area, security officials there said.

Warning of diplomatic consequences, Pakistan’s Foreign Ministry strongly condemned the attacks, the first since Parliament’s unanimous vote this month approving new guidelines for the country’s relationship with the United States. Some politicians said the drone strikes might set back already difficult negotiations over the reopening of vital NATO supply routes to Afghanistan that Pakistan blocked five months ago.

Last week, after two days of high-level talks in Islamabad, Pakistan told U.S. negotiators that it would not allow NATO convoys to cross its territory unless the United States unconditionally apologized for November airstrikes that killed 24 Pakistani soldiers near the Afghan border. Although the Obama administration has expressed regret for the killings, which it said were accidental, the Pentagon says both sides share blame.

Washington has made it clear that an apology will not be forthcoming, but officials from both governments say they are committed to ongoing talks. A Pentagon-led team of 10 negotiators, including State Department and White House officials, remains in Islamabad to focus on getting the NATO supply lines open.

“We haven't found a solution yet, but everybody wants to find one,” said one U.S. official, speaking on the condition of anonymity because of the sensitivity of the talks.

Since the terrorist attacks of Sept. 11, 2001, the two nations have maintained a bargain: Pakistan gets billions in aid and the United States gets supply routes and a counterterrorism ally. Part of the negotiations for the reopening of the border crossings also focus on the United States releasing $1.1 billion in overdue coalition support funds — money Pakistan is owed to cover its outlays for the battle against militants. Pakistan says the unpaid funds, with no U.S. payments made since mid-2010, total three times that amount.

The supply convoy routes from Pakistani seaports into land-locked Afghanistan not only support the war against the Taliban but also are crucial for the exit of U.S. troops and equipment in the combat-force withdrawal that is scheduled for completion by the end of 2014.

U.S. commanders have relied on stockpiles and goods brought in across Central Asia to the north while the Pakistani crossings have been closed. But the military has concluded that the tens of thousands of heavy vehicles and other materiel amassed over a decade of warfare in Afghanistan cannot be carried over those routes without enormous expense and effort, or within existing agreements with countries to the north.

In a process triggered by the November U.S. airstrikes on the Pakistani border posts, Pakistan’s Parliament on April 12 unanimously laid down foreign policy guidelines for future dealings with the United States, then passed them to the government of President Asif Ali Zardari for enforcement. The “terms of engagement” called for an immediate end to the CIA drone strikes, which Parliament had twice demanded in recent years, to no effect.

But this time, the civilian leaders acted with more authority than ever before in the nation’s 64-year history. The military, which conducted all previous Pakistani foreign relations, stood back to give the lawmakers and the government room to formulate key policies and negotiate with the United States.

The guidelines also said the government should seek an apology for “the condemnable and unprovoked” border attack by U.S. helicopters and fighter jets in November. At various times since November, the White House had considered making such an apology, but after militant attacks in Kabul on April 15 — blamed on the Pakistan-based Haqqani insurgent network — the United States ruled that out.

The resumption of the drone strikes — while not unexpected, given their efficiency and effectiveness — highlights a schism in the U.S. approach to Pakistan.

“When a duly elected democratic Parliament says three times not to do this, and the U.S. keeps doing it, it undermines democracy,” said a Pakistani government official, speaking on the condition of anonymity to preserve diplomatic relationships. “These drone strikes may kill terrorists, but the net loser is freedom and democracy.”

Prominent politicians predicted that the new drone strikes, the first inside Pakistan since March 30, would provoke a backlash against further negotiations on the supply lines and stir outcries that the United States has no regard for Pakistan’s sovereignty.

“There will be repercussions whether in the government or in the public or in the Parliament,” said Aftab Khan Sherpao, a National Assembly member who sat on the committee that drafted the guidelines. “In no case would we allow the NATO supplies now.”

Others saw the drone attacks as a provocation that undermined any notion that the United States had engaged in sincere, meaningful talks last week.

“The CIA could have opted not to go for a drone strike at such a crucial time, when senior U.S. officials are trying hard to iron out differences with Pakistan,” said Sheik Waqas Akram, a member of Prime Minister Yousuf Raza Gilani’s cabinet. “It shows that it has no regard for the Pakistani Parliament’s resolution.”

The target of Sunday’s attack was in Miran Shah, the largest town in North Waziristan and a base of operations for extremist groups including al-Qaeda and the Haqqani network. A senior U.S. official said intelligence had indicated that operatives there were “preparing explosives for use in attacks in Afghanistan, like the high-profile attacks in Kabul” on April 15.

The official spoke on the condition of anonymity to discuss the CIA’s covert drone program.

“Only individuals working directly on the explosives were killed or injured in this action, which we know with certainty helped protect Afghan and American lives,” the official said.

But Pakistan, in a statement late Sunday, called the attacks illegal and “violative of its territorial integrity and sovereignty.”

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