The $600 million sale aids Taiwan's "continuing efforts to modernize its armed forces and to maintain a credible defensive capability," the State Department said.

It will also assist in maintaining political stability and the military balance in the region, the department said in a statement.

The sale covers four drones, ground stations, and associated surveillance and communications equipment, but not the bombs or missiles usually associated with it.

The drones deal comes on the heel of several other major arms packages to Taiwan announced in recent weeks worth $4.2 billion, including potent Harpoon anti-ship missiles, air-launched SLAM-ER cruise missiles, air reconnaissance technology and mobile light rocket launchers.

The sales have angered Beijing, which regards Taiwan as a breakaway province since it split from mainland China under an exiled government seven decades ago.

While Taiwan has for decades fallen back on an implicit US security guarantee, Washington has urged it to strengthen its own capabilities to resist an effort by China to forcibly retake it.

China's military in recent months has simulated amphibious landings on Taiwan-like territory and repeatedly flown aircraft into the island's airspace.

The US military has used the unmanned Reapers, made by General Atomics, for long, high-altitude reconnaissance missions and pinpoint attacks and assassinations of jihadists in the Middle East and Afghanistan.

The sale is the first after the US government decided in July to diverge partly from the 1987 Missile Technology Control Regime, in which 35 countries agreed to restrict the sales of unmanned weapons delivery systems.

The decision was to permit the export of medium-speed drones like the Reaper that had been blocked by the agreement.