There are up to 200,000 small, untracked pieces of man-made debris that could threaten manned spacecraft, an expert said Tuesday.

"Space Command only tracks objects larger than a baseball," Theresa Hitchens, director of the Washington-based Center for Defense Information, told UPI.

"But there are between 100,000 and 200,000 pieces of space debris it doesn't track between the size of a baseball and a marble. And there are literally millions of smaller bios of debris than that," she said.

"NASA released a study earlier this year warning that the chances of the International Space Station or the Space Shuttle suffering a catastrophic accident from a collision with a piece of orbiting (man-made) space debris is only one in 200," Hitchens said.

"That's a shocking number. They hope to bring the figure down to a one in 600 chance."

The U.S. Air Force's Space Command currently tracks 13,000 man-made objects in space on a continual basis, of which only 6 percent are satellites. But Space Command only tracks objects larger than a baseball, Hitchens said.