The Pentagon used a missile to shoot down the satellite
Military operatives had only a 10-second window to hit the satellite - USA 193 - which lost control shortly after it was launched in December 2006.
Officials said they were worried fuel on board could pose a threat to humans.
But Russia suspects the operation was a cover to test anti-satellite technology under the US missile defence programme.The US denies the operation was a response to an anti-satellite test carried out by China last year, which prompted fears of a space arms race.
The SM-3 missile was fired from the USS Lake Erie in the Pacific at about 10:26 EST and hit the bus-sized satellite about 133 nautical miles above the ocean, the Pentagon said in a statement.
"A network of land, air, sea and space-based sensors confirms that the U.S. military intercepted a nonfunctioning National Reconnaissance Office satellite which was in its final orbits before entering the earth's atmosphere," it said.
"Confirmation that the fuel tank has been fragmented should be available within 24 hours," the statement said.
"Due to the relatively low altitude of the satellite at the time of the engagement, debris will begin to reenter the earth's atmosphere immediately," it added.
"Nearly all of the debris will burn up on reentry within 24-48 hours and the remaining debris should reenter within 40 days."watch: US shoots down spy satellite