The US State Department has approved the sale of three unmanned drones worth $1.2 billion to Japan, the Pentagon said on Friday.

Lawmakers have 15 days to block the sale, although such action is rare. Once the deal has cleared that hurdle, Japan and the US government can negotiate the actual sale.

The Defence Security Cooperation Agency, which oversees foreign arms sales, told lawmakers the Government of Japan had asked to buy three Global Hawk drones including parts and logistical support.

The drones "will significantly enhance Japan's intelligence, surveillance, and reconnaissance (ISR) capabilities and help ensure that Japan is able to continue to monitor and deter regional threats," the agency said in a notice to lawmakers that was posted on its website.

The prime contractor on the deal would be Northrop Grumman Corp.

Japan has long been mired in a territorial dispute with China over a group of tiny, uninhabited East China Sea islands.

In the South China Sea, Japan has been helping build the military capacity of friendly nations with claims to parts of the waterway.

On Friday, Japanese Prime Minister Shinzo Abe announced that he may consider a request from the Philippines for large coast guard ships to patrol the South China Sea.