US President George W. Bush is set to outline a dramatic shift in US space policy targeting a return to the moon and eventual manned mission to Mars, even as critics say a soaring deficit makes the goal unrealistic.
The proposal to replace aging US space shuttles with a new generation spacecraft could give Mr Bush a big-picture issue for his gathering re-election campaign and a theme for a potential second term.
Supporters and critics alike say Mr Bush's proposal would also help extend US military supremacy further into space, at a time China, a growing strategic power, is planning a series of lunar exploration missions.
"You always want the (strategic) high ground," US Republican Senator Sam Brownback of Kansas, chairman Senate commerce subcommittee on science, technology and space, said. He said he was "excited" about Mr Bush's proposal.
Bush is scheduled to speak at 8.15 p.m. Irish time at NASA headquarters in Washington. The National Aeronautics and Space Administration was shaken by the loss of the space shuttle Columbia on February 1st last year and has been seeking a way forward since.
Administration officials say Mr Bush will propose landing an unmanned spacecraft on the moon this decade. Humans would return to the moon's surface in the middle of the next decade, after an absence since December 1972.
The United States would establish a presence on the moon as a stepping stone to an eventual manned mission to Mars. The United States is the only country to land humans on the moon, beginning in 1969.
Mr Bush is to propose an increase in NASA's budget, now about $15 billion, by five per cent a year over the next three years, officials said. Other resources would be reallocated, including $3.5 billion a year for the space shuttle once it is retired on completion of the International Space Station.