Two US firms are in discussions on forming a team that will compete to build spacecraft able to take humans to the Moon, Mars and possibly beyond.
Boeing and Northrop Grumman have taken the first step towards putting together a team that will bid to build Nasa's Crew Exploration Vehicle (CEV).
The CEV was announced by President Bush in his "Moon to Mars" speech this year.
It is likely to be based on the module and capsule concept used by the US space agency Apollo and Gemini missions.
Boeing gave the BBC News website an exclusive look at new artwork of a potential design for the CEV.
The company stressed, however, that the concept does not reflect any design which a possible Boeing-Northrop team would come up with. It is merely illustrative of the sort of craft that may come out of the project.
Boeing and Northrop have not yet agreed to team up for bidding on the work.
But they have signed a "memorandum of agreement" that outlines the possible structure of such a team. The move is a further sign that the US space agency's Project Constellation is gathering pace.
Such a team could bid not only for the CEV but other elements in Project Constellation - a planned programme of human and robotic space missions that will take astronauts to the Moon, Mars and elsewhere in the Solar System.
The contractors are amongst 11 firms currently engaged in Nasa Concept Exploration and Refinement (CER) study contracts to define system requirements and architecture for Project Constellation.
Under an initial development phase, the CEV - which would replace the space shuttle - will demonstrate its ability to operate safely with astronauts in low-Earth orbit.
But it will subsequently expand its activities to include transporting crew to Earth's large, natural satellite and to the Red Planet.