Washington: US space agency NASA plans to create a permanent, manned lunar outpost on the moon's north or south pole when it returns there late in the next decade.

The base, which could span five kilometres, would be built on one of the poles because they provide light to the outpost for the longest amount of time, NASA Deputy Administrator Shana Dale said at a news conference at the Kennedy Space Centre in Florida yesterday (Dec 4, 2006).

The temperature at the poles is also more moderate than on other parts of the moon, but NASA said it did not yet know enough about the structure of the lunar poles to decide on the location for the outpost.

"We study right now the features we need," Associate Administrator Scott Horowitz said. "As we get more knowledge, we get deeper into design."

The lunar outpost will serve as a base for possible flights to Mars. Teams of four astronauts are expected to take their first steps on the moon by 2020 - 48 years after the last lunar landing.

NASA would be responsible for building up infrastructure and communication at the base, though other elements could be constructed by private companies and other space agencies.

"We are developing a system that has flexibility," Dale said.

NASA called on private companies to participate in the project to help bolster the agency's meagre budget of $16.23 billion.