Google Inc executives Larry Page and Eric Schmidt and filmmaker James Cameron are among those bankrolling a venture to survey and eventually extract precious metals and rare minerals from asteroids that orbit near Earth, the company said on Tuesday.

Planetary Resources, based in Bellevue, Washington, initially will focus on developing and selling extremely low-cost robotic spacecraft for surveying missions.

A demonstration mission in orbit around Earth is expected to be launched within two years, said company co-founders Peter Diamandis and Eric Anderson.

Planetary Resources' aim is to open deep-space exploration to private industry, much like the $10 million Ansari X Prize competition, which Diamandis created.

Planetary Resources' first customers are likely to be science agencies, such as NASA, as well as private research institutes.

Within five to 10 years, however, the company expects to progress from selling observation platforms in orbit around Earth to prospecting services. It plans to tap some of the thousands of asteroids that pass relatively close to Earth and extract their raw materials.

Not all missions would return precious metals and minerals to Earth. In addition to mining for platinum and other precious metals, the company plans to tap asteroids' water to supply orbiting fuel depots, which could be used by NASA and others for robotic and human space missions.

"We have a long view. We're not expecting this company to be an overnight financial home run. This is going to take time," Anderson said.

Planetary Resources declined to discuss specifics about how and when asteroid mining would begin. A 30-meter long (98-foot) asteroid can hold as much as $25 billion to $50 billion worth of platinum at today's prices, Diamandis said.

The company's first step is to develop technologies to cut the cost of deep-space robotic probes to one-tenth to one-hundredth the cost of current space missions, which run hundreds of millions of dollars, Diamandis said.