A $200 quadcopter drone has been shot out of the sky by a $4 million Patriot missile in an unidentified country, a US general has revealed.

General David Perkins told an Association of the United States Army (AUSA) conference that a "very close ally" of the US "dealing with an adversary" used the highly expensive missile to destroy the tiny drone.

"That worked. They got it," Perkins said in a speech posted on YouTube earlier this week.

"That quadcopter that cost 200 bucks from Amazon.com did not stand a chance against a Patriot."

"If I'm the enemy I'm thinking, 'Hey, I'm just going to get on eBay and buy as many of these $300 quadcopters as I can, and expend all the Patriot missiles out there."

While Perkins did not reveal what country used the Patriot missile, it could only be one of the Netherlands, Japan, Germany, Israel, Saudi Arabia, Kuwait, Taiwan, Greece, Spain, South Korea, the UAE or Qatar.

The Patriot missile is designed to destroy cruise missiles, ballistic missiles, rockets or enemy planes in the air.

Patriot missiles in Japan (left) and being tested in South Korea (right). (AAP)