President George W. Bush wants a 5 percent hike in NASA's annual budget for the next three years to begin plans for a base on the moon and a manned expedition to Mars.

A senior administration official said some money will come from phasing out the space shuttle and ending U.S. obligations to the International Space Station. The shuttle costs about $4 billion a year; the space station, about $1 billion.

The official said Bush will outline his plan in a speech Wednesday. The president will call for a permanent moon base within two decades and astronauts on Mars sometime after 2030.

A 5 percent increase in NASA's $15.5 billion budget would amount to $775 million in the first year, $813 million in the second year and $854 million in the third year.

Earlier, a space expert said he's "quite unimpressed" by the plans for future space missions.

Iowa physicist James Van Allen argues that such manned missions have become too costly -- and that better results could be gained by using robotic spacecraft.

Van Allen is considered one of the founding fathers of space exploration. The Van Allen Belts of intense radiation that circle the Earth are named after him.

Van Allen says that, these days, manned space flights have become "uninteresting except when disasters occur." He says people must have the courage to say, "Let's terminate human spaceflight."