Amazon has warned the Federal Aviation Authority (FAA) that if it doesn’t relax its attitude towards drone regulation then the internet giant will be forced to move its research teams out of the country.

"Without the ability to test outdoors in the United States soon, we will have no choice but to divert even more of our [drone] research and development resources abroad," said Amazon’s vice president of global public policy Paul Misener in a letter to the FAA seen by The Wall Street Journal. "I fear the FAA may be questioning the fundamental benefits of keeping [drone] technology innovation in the United States," said Misener.

Amazon is already experimenting with drones in the UK

Amazon’s plan to introduce delivery by drone in its experimental Prime Air program has already been hamstrung by FAA regulations. Current rules make the commercial use of drones in the US — including test flights — illegal, and a planned overhaul of the law set to arrive in early 2015 could be even more restrictive, with licenses only issued after dozens of hours of flight in manned aircraft.

Amazon has already begun exporting its research and is currently testing drones in Cambridge, England, where experimental flights don't require a special license and pilots are only expected to follow general rules such as staying away from large crowds and airports. The UK has already issued more than 300 licenses for commercial drone use with the majority used for photography and filming.