Pakistani officials are considering pulling out of NATO's annual summit in Chicago next month in protest over Sunday's U.S airstrike along the country's border with Afghanistan.
Islamabad is weighing the move after Sunday's airstrike by a U.S. drone in the city of Miranshah, the capital of North Waziristan, according to reports in the Pakistani press.
The possibility of future cooperation between Islamabad and Washington in Afghanistan and elsewhere in the region has become considerably more muddled in the aftermath of Sunday's airstrike.
"Such attacks are in total contravention of international law and established norms of interstate relations," according to a release by Pakistan's interior ministry.
Unmanned airstrikes by CIA-operated drones have become an integral part in the White House's campaign against international terror groups including al Qaeda and the Taliban. The number of clandestine airstrikes has surged under the Obama administration, taking out suspected terror targets in Yemen, Somalia and Pakistan.
But their use has roiled foreign governments, who claim the attacks are an affront to their national sovereignty.
Should Pakistan opt out of the NATO summit in May, it could be a major setback for U.S. and coalition efforts in the region.
At the summit, American officials are planning to finalize a pact with Afghanistan to outline future U.S. involvement in the country after coalition forces leave in 2014.
The airstrike comes as relations between the two countries were beginning to thaw. Islamabad was in the midst of debating whether to re-open supply routes into Afghanistan to the United States prior to Sunday's attack.
In March, Gen. James Mattis, head of Central Command, met with Pakistan Army chief Gen. Ashfaq Parvez Kayani in Pakistan last month, as the debate over reopening the supply routes was taking place.
American diplomats had hoped that emerging goodwill would flow into the upcoming NATO summit. However, it is unclear what effect Pakistan's ban on the Chicago meeting would have on negotiations over the Afghan supply lines.
The Pakistani plan to open those routes back up to U.S. forces called for a ban on all U.S.-led unmanned airstrikes inside the country's borders.
The plan, approved by Pakistan's parliament, also bars any private security contractors from working inside Pakistan and bans the United States from carrying out "overt or covert operations" within the country's borders.
Supply routes through Pakistan have been closed to American forces since last November, when U.S. warplanes accidentally attacked a Pakistani border outpost, killing 24 soldiers.
Pakistan also cut off all military and intelligence ties with the United States as a result of the attack.