A killer asteroid whose target is Earth will likely go undetected because NASA doesn't have the funds to find it, media reported Tuesday.

NASA officials say the space agency is capable of finding nearly all the asteroids that might destroy Earth, but the price to find at least 90 percent of the 20,000 potentially hazardous asteroids and comets by 2020 would be about 1 billion U.S. dollars, according to a report NASA will release later this week.

The report was previewed Monday at a Planetary Defense Conference in Washington.

Congress in 2005 asked NASA to devise a plan to track most killer asteroids and propose how to deflect the potentially catastrophic ones.

"We know what to do, we just don't have the money," said Simon "Pete" Worden, director of NASA's Ames Research Center.

These asteroids are a threat even if they don't hit Earth because if they explode while close enough -- an event caused by heating in both the rock and the atmosphere -- the devastation from the shockwaves is still immense.

The explosion alone could have with the power of 100 million tons of dynamite, enough to devastate a state the size of Maryland.

The agency is already keeping track of objects at least about 1,100 meter in diameter that could wipe out most life on Earth, much like what is theorized to have happened to dinosaurs 65 million years ago. But even that search, which has located 769 asteroids and comets -- none of which is on course to hit Earth -- is behind schedule. It's supposed to be complete by the end of next year.

NASA needs to do more to locate other smaller, but still potentially dangerous space bodies. While an Italian observatory is doing some work, the United States is the only government with an asteroid-tracking program, NASA said.

"The decision of the agency is we just can't do anything about it right now," said Worden.

John Logsdon, space policy director at George Washington University, said a stepped-up search for such asteroids is needed.

"You can't deflect them if you can't find them," Logsdon said. "And we can't find things that can cause massive damage."