US predator drone
A US Air Force MQ-1 Predator, unmanned aerial vehicle, armed with AGM-114 Hellfire missilesReuters/US Air Force

The US is to sell armed drones to its allies and other countries it considers friendly.

The sales will come with a series of strict requirements that the buyers will have to fulfil, according to a new policy published by the US State Department.

Buyers will have to agree that the vehicles will only be used for military campaigns. The US will also review whether buyers are complying with the terms of sale.

The State Department did not say which countries would be considered for armed drone sales. Currently, only the UK has been allowed to buy armed unmanned aircraft from the US.

American legislators are currently considering whether to sell unarmed Predator drones to the United Arab Emirates.

Unnamed officials have been quoted in the US media as saying the State Department would reconsider requests from Italy and Turkey.

The US has become increasingly reliant on armed drones since the declaration of the so-called War on Terror. The unmanned vehicles were first used for bombing raids by George Bush but his successor Barack Obama has dramatically increased the use of drones for American operations in Pakistan, Yemen, Somalia and elsewhere.

Human rights groups have criticised drones for causing massive civilian casualties and a lack of unaccountability. The CIA and the White House rarely acknowledge if a drone strike has been carried out, although all drone strikes require presidential approval.

The policy change follows a two-year review, and has been crafted to make sure aircraft are being used responsibly and legally, the State Department said.

"The technology is here to stay," an unnamed department official told the Washington Post newspaper. "It's to our benefit to have certain allies and partners equipped appropriately."

The terms of sale would include an agreement that the armed drone would be used in accordance with international law and would not be used for unlawful surveillance.