WASHINGTON — The Bush administration is trying to convince foreign countries that the Pentagon's plan to shoot down a dying spy satellite is not a test of a program to kill their orbiting communications and intelligence capabilities.

The State Department has instructed U.S. diplomats around the world to inform their host governments that the operation, which could be conducted as early as next week from a Pearl Harbor-based Navy ship, is aimed solely at protecting people that could be affected by about 1,000 pounds of toxic fuel on the bus-sized satellite now hurtling toward Earth.

"Our role is to reassure nations around the world as to the nature of what we are tying to do," spokesman Sean McCormack said Friday. "It's an attempt to try to protect populations on the ground."

In a cable sent to all U.S. embassies abroad, diplomats were told to draw a clear distinction between the upcoming attempt and last year's test by China of a missile specifically designed to take out satellites, which was criticized by the United States and other countries.

"This particular action is different than any actions that, for example, the Chinese may have taken in testing an anti-satellite weapon," McCormack told reporters. "The missions are quite different and the technical aspects of the missions are quite different."

Other than intent, he said the key difference is that the Pentagon's planned shoot-down will be done at a much lower altitude than that of the Chinese, whose 2007 destruction of a satellite left a large debris field in orbit. The U.S. plan, it is hoped, will leave little in the way of debris that could complicate efforts to place future satellites in orbit.

U.S. officials said the satellite is carrying fuel called hydrazine that could injure or even kill people who are near it when it hits the ground. That reason alone, they said, persuaded President Bush to order the shoot-down.

The Pentagon has predicted a fairly high chance — as much as 80 percent — of hitting the satellite, which will be about 150 miles up before it enters Earth's atmosphere when a single missile will be fired from a Navy cruiser in the northern Pacific Ocean. If it misses, there may be a second shot, officials say.

Left alone, the satellite would be expected to hit Earth during the first week of March. About half of the 5,000-pound spacecraft would be expected to survive its blazing descent through the atmosphere and would scatter debris over several hundred miles.

Known by its military designation US 193, the satellite was launched in December 2006. It lost power and its central computer failed almost immediately afterward, leaving it uncontrollable. It carried a sophisticated and secret imaging sensor.