More than 9,000 asteroids whose orbit passes near Earth have already been discovered and another 900 or so are discovered every year.
Many of the space rocks are thought to contain valuable resources such as industrial metals (nickel and iron, for example), valuable platinum-like metals, silicon, water and gases.
Mining an asteroid and flying the material back for use on Earth would be wildly inefficient – the cost of returning metals from space would be greater than their terrestrial value.
But Deep Space Industries claims metals which would be worth just a few thousand dollars on Earth could be worth millions in space, where they could be used to manufacture parts for space stations and solar panel arrays.
A "3D printer" known as the MicroGravity Foundry will transform raw materials into complex metal parts using lasers to shape nickel into precise patterns, meaning it can create components in zero-gravity conditions, the company announced.
Mark Sonter, a director of DSI, said: "If you can retrieve some of this metal, manufacture it and deliver it to certain areas in space where it can be used, it is potentially extremely valuable material."
They could also provide fuel and equipment for the International Space Station and for future spacecraft on missions to Mars, avoiding the need to carry them from Earth.
Launching a "dry" mission to Mars which refills its fuel tanks after entering orbit would reduce costs by 90 per cent compared with a mission which is fully fuelled from the start, the company claimed.
Rare platinum-group metals could be harvested at the same time as other resources for sale back on Earth to generate additional profit, directors added.
Chairman Rick Tumlinson said: "We will only be visitors in space until we learn how to live off the land there.
"This is the Deep Space mission – to find, harvest and process the resources of space to help save our civilisation and support the expansion of humanity beyond the Earth – and doing so in a step by step manner that leverages off our space legacy to create an amazing and hopeful future for humanity."