The United States will now allow the sale of armed unmanned aerial systems to other countries on a case-by-case basis, the State Department said.

Any such sales would come with stringent conditions and only through the U.S. Foreign Military Sales program.

"As other nations begin to employ military UAS more regularly and as the nascent commercial UAS market emerges, the United States has a responsibility to ensure that sales, transfers, and subsequent use of all U.S.-origin UAS are responsible and consistent with U.S. national security and foreign policy interests, including economic security, as well as with U.S. values and international standards," the State Department said.

"As a result, the United States has established a new policy designed specifically for U.S.-origin military and commercial UAS. This new policy, governing the international sale, transfer and subsequent use of U.S.-origin military UAS, supplements and builds upon the U.S. Conventional Arms Transfer Policy and is consistent with the requirements of the Arms Export Control Act and the Foreign Assistance Act which govern all U.S. military transfers."

Among conditions of the new UAS export policy: countries would have to agree to use the systems in accordance with international law, including international humanitarian law and international human rights law; and armed and other advanced UAS used in operations involving force, could only do so "when there is a lawful basis for use of force" under international law.

Potential recipients would also have to agree not to use the systems in "unlawful surveillance or use of unlawful force" against their domestic populations.

U.S. commitments under the Missile Technology Control Regime remain, the department said.

Previous sales of unmanned aerial systems to NATO allies involved platforms used for intelligence, surveillance and reconnaissance, not those for armed missions.