Astronauts arriving from Earth in the Orion crew capsule will dock at the gateway, which will be in orbit around the Moon, before transferring to a lunar landing module and descending to the surface, the Guardian reported.
It will also double as a research outpost for astronauts who do not become Moonwalkers.
Maxar Technologies will build the Power and Propulsion Element (PPE), which is scheduled to launch in late 2022. The company is a privately owned manufacturer best known for building communications satellites.
The contract is worth $375 million (£295m) and Maxar will work with Blue Origin and Draper to deliver the spacecraft. Maxar won against competition from some of the biggest names in the US aerospace including Boeing and Lockheed Martin.
The PPE will power a utilization module, which has yet to be contracted but will serve as a small habitation space and docking node.
The Orion crew capsule is well into production, but the contract for the lunar lander is still to be awarded.