The U.S. Congress is encouraging Americans to scour the skies for asteroids that might threaten Earth. Lawmakers want to offer cash incentives.

The House of Representatives has passed legislation to reward amateur U.S. astronomers for discovering asteroids that could possibly collide with Earth. The U.S. Senate is considering an identical measure.

They would authorize the head of the U.S. space agency NASA to give $3,000 each year to a citizen who finds the biggest asteroid in a near-Earth orbit.

Sponsors of the legislation say there have been several near misses that would have proven catastrophic if the asteroids had struck. Scientists classify 160 of them as potentially hazardous.

They point out there would be time to develop technology to destroy an object if one were discovered a few decades before possible impact.

NASA and the University of Arizona operate professional near-Earth asteroid tracking programs in the United States and an international group called the Spaceguard Foundation coordinates global efforts. But the lawmakers point out that the scientific community relies heavily on backyard astronomers for help.

The Senate must also pass the asteroid hunting measure before President Bush can sign it into law.