MOSCOW - Debris from this week's satellite collision could circle Earth for up to 10,000 years, threatening many other satellites in an already-crowded area, Russia's Mission Control chief said Friday.

Vladimir Solovyov said Tuesday's smashup of a derelict Russian military satellite and a working U.S. Iridium commercial satellite occurred some 800 kilometers above Earth -- the busiest part of near-Earth space.

"800 kilometers is a very popular orbit which is used by Earth-tracking and communications satellites," Solovyov told reporters. "The clouds of debris pose a serious danger to them."

Solovyov told reporters even tiny fragments could pose a serious threat to spacecraft made of light alloys because both travel at such a high speed.

Most fragments are concentrated near the collision course, but Maj.-Gen. Alexander Yakushin, chief of staff of the Russian military's Space Forces, said some debris was thrown into other orbits, ranging from 500-1,300 kilometers above Earth.

The U.S. military already tracks 18,000 objects in orbit, but no one has any idea yet exactly how many extra pieces of space junk were generated by the collision or how big they might be. Space experts say the collision created hundreds of fragments, maybe thousands, if tiny pieces are included.

Meanwhile, there's no global air traffic control system that tracks the position of all satellites.

The U.S. military only monitors certain threats in space because it lacks the resources to do everything, said Maj. Regina Winchester, spokeswoman for U.S. Strategic Command, which oversees the military's Space Surveillance Network.

"With the amount of spacecraft and debris in orbit, the probability of collisions is going up more rapidly," said John Higginbotham, chief executive of Integral Systems Inc., a Lanham, Maryland-based company that runs ground support systems for satellites.

Tuesday's collision was the first high-speed impact between two intact spacecraft, NASA officials said. The Iridium craft weighed 560 kilograms, and the Russian craft nearly a ton.

Both NASA and Russia's Roscosmos agencies said, however, there was little risk to the international space station and its three crew members. The station orbits about 370 kilometers above Earth, far below the collision point.

Russian Mission Control spokesman Valery Lyndin noted the station's orbit has been adjusted in the past to dodge space debris, with Russian and U.S. space officials working together to perform such maneuvers.

Meanwhile, an unmanned Russian cargo ship docked smoothly Friday at the international space station delivering supplies for its three-member crew.

Lyndin said the Progress M-66 spacecraft delivered about 2.5 metric tonnes of water, food, fuel, oxygen and other supplies as well as a second new Russian-made, computerized space suit for space walks.

American astronauts Michael Fincke and Sandra Magnus are aboard the station along with Russian Yuri Lonchakov. The crew size will be doubled to six members later this year.