The success of U.S. drones in Iraq and Afghanistan has triggered a global arms race, raising concerns the remotely piloted aircraft could fall into unfriendly hands, military experts say.
The number of countries that have acquired or developed drones expanded to more than 75, up from about 40 in 2005, according to the Government Accountability Office, the investigative arm of Congress. Iran and China are among the countries that have fielded their own systems.
"People have seen the successes we've had," said Lt. Gen. Larry James, the Air Force's deputy chief of staff for intelligence, surveillance and reconnaissance.
The U.S. military has used drones extensively in Afghanistan, primarily to watch over enemy targets. Armed drones have been used to target terrorist leaders with missiles that are fired from miles away.
The United States is years ahead of the world in the technology of drones. Israel is also a leader in developing the unmanned aircraft.
American drones are equipped with sophisticated sensors and linked to a global network that allows their video feeds to be monitored from anywhere. Armed drones fire the latest in precision guided missiles.
Building an unmanned aircraft is only part of what is needed for a successful drone program.
"Just because you can build a remotely piloted aircraft doesn't mean you can put all this together and do something with it," James said.
Analysts warn that even a less-sophisticated drone can be dangerous. Such drones can be equipped with chemical or biological weapons or be used to provide intelligence about the location of American forces.
The GAO reports it is likely that foreign countries have used drones to spy on U.S. military activities overseas. The report did not provide specifics. "Even the less sophisticated technologies can provide useful tactical battlefield intelligence," said Thomas Melito, a GAO official.
Israeli aircraft recently shot down an Iranian-made drone launched by Hezbollah that had penetrated Israeli airspace. Hezbollah is a U.S.-designated terror group supported by Iran that has fought wars with Israel and carried out attacks on U.S. personnel.
Pakistan is attempting to acquire an armed-drone system, apparently with help from China, according to IHS Jane's, a security research firm.
Countries may be able to narrow the technology gap over the course of years. "We are dramatically ahead today, but people will look and learn," James said. "Over time, they will build capacity."
The U.S. State Department and Defense Department control exports of U.S. drone technology and equipment, and the United States has rejected requests from a growing number of countries seeking drone technology. Israel has sold drone equipment to India, Russia and Georgia, according to the GAO.
Some analysts contend that nations seek the drones as much for the clout they bring as any military utility they provide, since few countries have the sophisticated sensors or precision weapons that the United States employs.
"It's a prestige thing," said Micah Zenko, an analyst at the Council on Foreign Relations. "It doesn't provide you with much additional combat capability."