Bush won't propose sending Americans to Mars anytime soon; rather, he envisions preparing for the mission more than a decade from now, one official said.
In addition to a returning trip to the moon for the first time since December 1972, the president also wants to build a permanent space station there.
Three senior officials said Bush wants to aggressively reinvigorate the space program, which has been demoralized by a series of setbacks, including the space shuttle disaster last February that killed seven astronauts.
The officials, speaking on condition of anonymity, said Bush's announcement would come in the middle of next week.
Bush has been expected to propose a bold new space mission in an effort to rally Americans around a unifying theme as he campaigns for re-election.
Many insiders had speculated he might set forth goals at the 100th anniversary of the Wright brothers' famed flight last month in North Carolina. Instead, he said only that America would continue to lead the world in aviation.
Earlier, White House spokesman Scott McClellan told reporters traveling with Bush in Florida that the president would make an announcement about space next week, but he declined to give details.
House Science Committee spokeswoman Heidi Tringe said lawmakers on the panel "haven't been briefed on the specifics" but expected an announcement.
Rep. Ralph Hall, R-Texas, a member of the House Science Committee, said he welcomed the move because he has tried to get the president more interested in space exploration.
"I had the feeling the last 2½ years people would rather make a trip to the grocery store grocery store than a trip to the moon because of the economy," Hall said. "As things are turning around, we need to stay in touch with space" and the science spinoffs it provides.
This week, NASA landed a six-wheeled robot on Mars to study the planet. However, the Spirit rover is stuck because the air bags that cushioned its landing are obstructing its movement.
Asked Wednesday whether the success of the Mars rovers could lead to a human mission to Mars, NASA Administrator Sean O'Keefe said, "The rovers are a precursor mission kind of an advance team to figuring out what the conditions are on the planet, and once we figure out how to deal with the human effects, we can then send humans to explore in real time."
While answering questions on the White House Web site, O'Keefe said interplanetary exploration depends on "what we learn and whether we can develop the power and ... propulsion capabilities necessary to get there faster and stay longer and potentially support humans in doing so."
No one, least of all members of Congress, knows how NASA would pay for lunar camps or Mars expeditions. The last time a president pushed such ambitious ideas the first President Bush on the 20th anniversary of the first manned moon landing the estimated price tag was $400 billion to $500 billion.
The moon is just three days away while Mars is at least six months away, and the lunar surface therefore could be a safe place to shake out Martian equipment. Observatories also could be built on the moon, and mining camps could be set up to gather helium-3 for conversion into fuel for use back on Earth.
House Majority Leader Tom DeLay, R-Texas, among others, has called for an expansion of the U.S. space program, including a return to the moon. The United States put 12 men on the moon between 1969 through 1972.
An interagency task force led by Vice President Dick Cheney has been considering options for a space mission since summer.
Former Ohio Sen. John Glenn, the first American to orbit the Earth, has said that before deciding to race off to the moon or Mars, the nation needs to complete the international space station and provide the taxi service to accommodate a full crew of six or seven. The station currently houses two.
At the same time, Glenn has said, NASA could be laying out a long-term plan, setting a loose timetable and investing in the engineering challenges of sending people to Mars. The only sensible reason for going to the moon first, he says, would be to test the technology for a Mars trip.