The US Pentagon is planning a new 'weapon of mass destruction' that involves thousands of drones that strike by air, land and water to destroy enemy defenses - but experts fear humans could lose control of the 'swarms.'

The top-secret project, dubbed AMASS (Autonomous Multi-Domain Adaptive Swarms-of-Swarms), would represent automated warfare on an unprecedented scale.

AMASS is still in the planning stages, but DARPA (Defense Advanced Research Project Agency) has been collecting bids from suppliers for the $78 million contract.

Small drones would be equipped with weapons and tools for navigation and communication, along with abilities ranging from radar jamming to launching lethal attacks.

While the technology would change how the US goes to war, experts in the industry raise concerns.

Zachary Kallenborn, a policy fellow at George Mason University in Virginia, said: 'As the swarm grows in size, it'll become virtually impossible for humans to manage the decisions.'

The US military has been using unmanned aerial vehicles on the battlefield since 2001, but has since evolved to employ smaller, stealthier machines to sneak over enemy lines to destroy camps or even jam opposing technologies.

And DARPA's AMASS would release thousands at once to undertake several tasks with little to no human intervention.

Speaking on a panel at Cornell last year, U.S. Army Lt. Col. Paul Lushenko said: 'Drones can aid, they can watch, and they can kill.'

'In theory, AMASS could be entirely non-lethal, carrying out jamming or other non-kinetic attacks in support of other platforms that actually destroy the defences,' said Kallenborn.

'I think that's unlikely though.'

The AMASS project's development would involve experiments with both real and virtual drone swarms, then gradually increasing their size and complexity.

According to DARPA federal contract documents, 'AMASS will create the ability to dynamically command and control (C2) unmanned, autonomous swarms of various types (i.e., swarms-of-swarms) with a common C2 language.'

DARPA said the swarms will be assigned 'through an optimization process that considers mission objectives, priorities, risks, resource availability, swarm capabilities, and timing.'

A DARPA spokesperson told the SWNS that the aim is to keep humans making key decisions, with drones waiting for permission to act if communications fail.

According to the US Department of Defense's policy on autonomous weapons (known as Directive 3000.09): 'Autonomous and semi-autonomous weapon systems will be designed to allow commanders and operators to exercise appropriate levels of human judgment over the use of force.'

But Kallenborn is skeptical: 'As the swarm grows in size, it'll become virtually impossible for humans to manage the decisions. Autonomy and AI will be needed to make those decisions.'

AMASS is not the only DARPA project in the works involving swarms of autonomous drones.

For years, it has been developing project OFFSET (the OFFensive Swarm-Enabled Tactics Program), which would involve up to 250 aerial and land drones.

The first true drone swarm effort was conducted by Israel in a 2021 conflict with Hamas in Gaza. But nothing on the scale of AMASS.