Washington ? President Bush will seek to boost NASA’s budget by $1 billion over five years to help pay for his plan to put a base on the moon and to mount a manned expedition to Mars later in the century, a senior administration official said Tuesday.

Bush’s election-year vision calls for establishing a permanent presence on the moon within two decades and putting astronauts on Mars sometime after 2030, a second official said.

“The spirit is going to be one of continued exploration … seeking new horizons and investing in a program that … meets that objective,” Bush told reporters Tuesday during a trip to Mexico.

To pay for the space initiative, which he will outline in a speech this afternoon, Bush would increase NASA’s budget by $200 million a year for five years.

Congressional negotiators last year agreed to a NASA budget of nearly $15.5 billion for fiscal 2004, which began Oct. 1, 2003. That’s a $90 million boost over the previous year. The measure, part of a broad-based spending bill, was passed by the House and awaits approval by the Senate.

The administration said part of the funding for the moon-Mars initiative would come from reallocation of money already in NASA’s budget, including phasing out of the space shuttle and quickly concluding the U.S. obligations to the International Space Station. The shuttle now costs NASA about $4 billion a year and the station about $1 billion.

Bush’s father, the first President Bush, proposed a more muted project, which would have aimed at putting Americans on Mars without mention of a moon base. The cost of that enterprise was projected at $400 billion to $500 billion in 1989 dollars, far too rich for Congress.

The current president’s plan, one official said, calls for sending exploring robots to the moon by 2008, landing humans there by 2020 and then launching a Mars expedition after 2030. He envisions using the moon as a steppingstone to deeper space exploration, to Mars and perhaps beyond.

He said the president’s address will give broad outlines to the moon-Mars plan, leaving details to be worked out later.

The officials spoke on condition of anonymity.

Experts said that an effort to return to the moon would require building new spacecraft. They said the eventual plan could include sending robot craft to the moon and later to Mars to cache supplies for use later by human explorers.

Hakimuddin Husein looks at a Mars exhibit while visiting Space Center Houston. Today, President Bush is scheduled to outline his proposals for space exploration and announce a plan to boost NASA's budget by billion over five years.

Some have suggested that such an ambitious program would require nuclear power to energize the lunar colony and later to provide dependable electricity for any extended Mars expedition.

NASA already is working to develop an electric-ion rocket that could be used to speed the months-long trip to Mars.

Much of the equipment and techniques needed for a Mars venture could first be tested at a lunar base.

The moon, with its gravity just one-sixth of the Earth’s, might also be used as a jumping off point for voyages beyond Earth’s orbit, such as to Mars or to asteroids.

Some experts have proposed that a colony on the moon could exploit mineral resources that are thought to be on the lunar surface. It’s known that lunar soils contain helium-3, a potential fuel. Some studies also have suggested the moon may have water that could be chemically split to obtain hydrogen and oxygen, a combination that can be used as a rocket propellant. The oxygen could be used for an atmosphere inside sealed shelters.