Israel's high-tech defense industry leads the world in exporting unmanned aerial vehicles, a new study says, while UAV designers are reported to be moving toward developing drones so advanced they could replace manned aircraft.

The international business consultancy Frost and Sullivan reports that over the last eight years Israeli manufacturers have sold UAVs worth more than $4.6 billion.

Just more than half of the deals in 2005-12 were with European states, primarily Germany, Poland, the Netherlands, Russia and Spain.

A particularly large number of drones supplied to Britain's Watchkeeper UAV program, which is a joint project between Israel's Elbit Systems and the French defense multinational Thales. Watchkeeper drones are based on Elbit's Hermes 450 aircraft.

One-third of Israeli exports went to the Asia-Pacific region, including India, a major buyer of Israeli defense systems, and Azerbaijan.

Israel, which pioneered UAV technology in the 1970s, has steadily cultivated military and intelligence links with the former Soviet republic, Iran's northern neighbor, and has become a key arms supplier to the oil-rich Caspian state.

In addition to exports, Israeli defense firms set up subsidiaries in consumer countries "to target markets, rather than expand local manufacturing," Israel's Haaretz daily observed in 2009.

One example is the Aerostar and Orbiter 2M aerial drones being manufactured in Azerbaijan by Azad Systems Co., a joint venture between Israel's Aeronautics Defense Systems and the Azeri Defense Ministry.

The Stockholm International Peace Research Institute reported a few weeks ago that Israeli companies were behind 41 percent of all UAVs exported from 2001-11. Those Israeli exports went to 24 countries, including the United States.

Frost and Sullivan noted that the overall total of Israeli UAV exports didn't include a $100 million deal by state-owned Israel Aerospace Industries with India to upgrade its Heron drones.

Defense News website says India, one of the biggest markets for the Heron, operates 60 of the IAI craft acquired in several deals together worth $1 billion -- and wants more.

The Heron can stay aloft for 40 hours at 30,000 feet, and carries a formidable array of sensors and avionics.

Israel and predominantly Hindu India are both battling Islamist militants, so their defense links are expected to grow. New Delhi's expanding defense ties with Israel underline its commitment to break India's longtime dependence on Russian weapons systems.

Eleven percent of the UAV sales, valued at $508 million, involved Latin American states, which in recent years have become an Israeli target for military deals.

All told, Israel military exports in 2005-2 were worth about $6.1 billion a year, with UAV sales totaling some $578 annually.

Israel is a major operator of UAVs, with three air force squadrons equipped with Heron, Hermes 450 and Searcher craft, as well as the giant Eitan with a wingspan of 83 feet.

Israel, with the most advanced defense industry in the Middle East, is in the forefront of the rapidly expanding drone business that's changing the way wars will be fought for decades to come.

IAI, Elbit and Aeronautics Defense Systems are developing new and more agile unmanned aerial vehicles, as well as ground and seaborne drones.

Israel's export volume is expected to expand as production costs are relatively low. Israeli industry officials boast that it's now significantly cheaper to buy an advanced UAV than it is to train an air force pilot.

Indeed officials say that within a few decades Israeli UAVs will be able to carry out virtually every battlefield function currently conducted by piloted aircraft.

"In recent years, there have been more pilotless sorties than piloted ones in the air force," observed Ophir Shoham, a reserve brigadier general who heads the Defense Ministry's Research and Development division.

"Within a few years there will be a number of operational missions that we'll be able to carry out with a small number of unmanned devices," he told the Haaretz daily in April.

"That's the direction we're taking. Robots are not about to replace combat soldiers -- that's a bit far off -- but yes, we'll operate unmanned vehicles on the ground against highly dangerous targets.

"I refer to targets in enemy territory against which we can send such vehicles remotely, as a kind of forward guard -- vehicles that both observe and shoot," he said. "We'll witness this in the foreseeable future."