The White House announced that President Donald Trump had approved a move to diverge partly from the 1987 Missile Technology Control Regime, in which 35 countries agreed to restrict the sales of unmanned weapons delivery systems.

The MTCR was aimed at controlling the spread of missiles that could deliver large payload like nuclear weapons.

But it also covered armed drones, at the time not a major component of armed conflict as they are now.

The change ordered by Trump will reclassify armed drones from technology whose export is severely restricted to a category that can be considered on a case-by-case basis.

The drones in the category must have a maximum airspeed of less than 800 kilometers per hour, which will allow sales of the Reaper and Predator drones used by the US military, as well as others made by US defense manufacturers.

"The MTCR's standards are more than three decades old," the White House said in a statement.

"Not only do these outdated standards give an unfair advantage to countries outside of the MTCR and hurt United States industry, they also hinder our deterrence capability abroad by handicapping our partners and allies with subpar technology."

The White House statement said two years of talks had failed to reform the MTCR.

The move has worried arms control advocates who say the US sale of advanced drones to more countries could fuel the global arms race.

"The Trump administration has once again weakened international export controls on the export of lethal drones," said Senator Bob Menendez in a statement.

"This reckless decision makes it more likely that we will export some of our most deadly weaponry to human rights abusers across the world," he said.