The firm has been waiting since July for approval from the Federal Aviation Administration (FAA) to test drones near Seattle, reports Reuters. Amazon announced proposals for a drone delivery service called Amazon Prime Air in December 2013.
The FAA has been contacted by the BBC for comment. "Without approval of our testing in the United States, we will be forced to continue expanding our Prime Air R&D footprint abroad," wrote Paul Misener, Amazon's vice president of global public policy, in a letter to the FAA.
Amazon wants to use small drones to deliver packages up to 2.3kg (5lb) in weight. The service would enable customers to receive a purchase within 30 minutes of placing an order.
I'm not sure that this threat will spur anyone into action. I suspect that the US will be glad to have development (and the risks associated with it) conducted overseas because, at the end of the day, it will still be used to serve the US market no matter where it is developed.