The United States will send humans back to the moon by 2020, President George W Bush said on Wednesday.
The moon will be used as a steppingstone for missions to Mars and beyond, he said.
"We do not know where this journey will end, yet we know this -- human beings are headed into the cosmos," Bush said. "Mankind is drawn to the heavens for the same reason we were once drawn into unknown lands and across the open sea. We choose to explore space because doing so improves our lives and lifts our national spirit."
Bush said establishing an extended human presence on the moon could vastly reduce the cost of further space exploration, making possible ever more ambitious missions. "Lifting heavy spacecraft and fuel out of the earth's gravity is expensive. Spacecraft assembled and provisioned on the moon could escape its far lower gravity using far less energy and thus far less cost," he said at the NASA headquarters in Washington.
"With the experience and knowledge gained on the moon, we will then be ready to take the next steps of space exploration -- human missions to Mars and to worlds beyond," he said.
According to reports, the White House estimates that the moon plan will require an extra $12 billion over the next five years.
It said $11 bn of that would come from reallocation of NASA funds and the president would ask Congress to approve the rest.
Bush would ask for a 5% yearly increase in NASA $15.4 bn annual budget for the next three years, followed by 1% in subsequent years.
Bush said the US would welcome international participation in the project.
"We'll invite other nations to share the challenges and opportunities of this new era of discovery," he said. "The vision I've outlined today is a journey, not a race, and I call on other nations to join us on this journey, in the spirit of cooperation and friendship."
The US will also wrap up its obligations on building the International Space Station by 2010, after which it will retire the remaining three space shuttles used to build and service the station, Bush said.
The initial spurt of new funding will be used to begin work on a "crew exploration vehicle".