Pakistani officials say the first trucks carrying NATO supplies have crossed into Afghanistan, following a U.S.-Pakistani deal announced this week that ended Islamabad's months-long blockade.

Local officials in southwestern Pakistan say the supplies crossed the border at Chaman in Baluchistan province Thursday. The crossing comes days after U.S. Secretary of State Hillary Clinton said the United States “is sorry for the Pakistani military's losses.”

Pakistan had closed the supply lines after a U.S. airstrike mistakenly killed 24 of its soldiers near the Afghan border last November. In the nearly eight months that followed, Pakistan's demands for a full apology and an end to U.S. drone strikes in its territory deadlocked negotiations between the two countries to reopen the routes.

On Thursday, Pakistani Prime Minister Raza Pervez Ashraf defended his government's decision to reopen the supply lines, saying it would help Afghanistan's stability which would help Pakistan's prosperity. Islamabad also has said it hopes to help facilitate Afghanistan's transition process as international combat troops leave Afghanistan by the end of 2014.

But the issue of security remains. The convoys are a favorite target for militants, and the Pakistani Taliban has vowed to continue its attacks. The recent threat prompted Pakistan's trucker's association to ask the government for added protection.

An alliance of more than 40 right-wing and religious parties known as the Defense Council of Pakistan also has condemned the government's decision and announced it is organizing a protest march in Islamabad Sunday. During the suspension, the alliance has held rallies across Pakistan in all major cities to warn the government against resuming the shipments.