A miniature "kamikaze" drone designed to quietly hover in the sky before dive-bombing and slamming into a human target will soon be part of the US Army's arsenal, officials say.

Dubbed the "Switchblade," the robotic aircraft represents the latest attempt by the United States to refine how it takes out suspected militants.

Weighing less than two kilos, the drone is small enough to fit into a soldier's backpack and is launched from a tube, with wings quickly folding out as it soars into the air, according to manufacturer AeroVironment.

Powered by a small electric motor, the Switchblade transmits video in real time from overhead, allowing a soldier to identify an enemy, the company said in a press release last month.

"Upon confirming the target using the live video feed, the operator then sends a command to the air vehicle to arm it and lock its trajectory onto the target," it said.

The drone then flies into the "target," detonating a small explosive.

The California-based firm also said the drone can be called off at the last moment, even after a kill mission has been ordered. That feature provides troops with "a level of control not available in other weapon systems," it said.

The United States currently uses larger Predator and Reaper drones to hunt down suspected militants in Pakistan and elsewhere.

The robotic planes fire powerful Hellfire missiles and drop heavy bombs that can cause civilian casualties and extensive damage, which has fueled popular anger with the United States in Pakistan.

In the war in Afghanistan, US and coalition troops fighting the the Taliban can call in artillery fire or air strikes from fighter jets and attack helicopters. But the heavy firepower has been blamed by Afghan leaders for claiming the lives of innocent civilians and strained US relations with Kabul.

The Switchblade, however, is touted as a way to avoid killing bystanders.

"Flying quietly at high speed the Switchblade delivers its onboard explosive payload with precision while minimizing collateral damage," the company said.

The US Army in June approved a $4.9 million contract for AeroVironment to supply the new drones as soon as possible. Officials have not said how many Switchblade drones were ordered or when the robotic weapons would make into the hands of US forces.

Human rights groups have raised concerns that the use of drones by the CIA has allowed the conduct of a secret assassination campaign abroad without public scrutiny and little oversight by lawmakers in Congress.