The European Space Agency says it will contribute key components for a future NASA mission to take humans around the moon within the next few years.
Astronauts haven't gone beyond a low orbit around Earth since 1972, when NASA ended its Apollo program.
The European Space Agency and aerospace company Airbus have already delivered a propulsion and supply module for an unmanned flight of NASA's new Orion spacecraft next year.
The agency said Wednesday that it and Airbus have now agreed with NASA to build a module for a second, manned mission that will fly around the moon as early as 2021.
Orion is eventually intended to expand human exploration to deep-space destinations such as Mars or asteroids.