Taking a page from Hollywood science fiction, the Pentagon said Thursday it will try to shoot down a dying, bus-size U.S. spy satellite loaded with toxic fuel on a collision course with the Earth. The military hopes to smash the satellite as soon as next week — just before it enters Earth's atmosphere — with a single missile fired from a Navy cruiser in the northern Pacific Ocean. The dramatic maneuver may well trigger international concerns, and U.S. officials have begun notifying other countries of the plan — stressing that it does not signal the start of a new American anti-satellite weapons program. Military and administration 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. "That is the only thing that breaks it out, that is worthy of taking extraordinary measures," said Gen. James Cartwright, vice chairman of the Joint Chiefs of Staff, during a Pentagon briefing. He predicted a fairly high chance — as much as 80 percent — of hitting the satellite, which will be about 150 miles up when the shot is fired. The window of opportunity for taking the satellite down, Cartwright said, opens in three or four days and lasts for about seven or eight days. "We'll take one shot and assess," he said. "This is the first time we've used a tactical missile to engage a spacecraft." Deputy National Security Adviser James Jeffrey discounted comparisons to an anti-satellite test conducted by the Chinese last year that triggered criticism from the U.S. and other countries. "This is all about trying to reduce the danger to human beings," Jeffrey said. "Specifically, there was enough of a risk for the president to be quite concerned about human life." There might also be unstated military aims, some outside the administration suggested. Similar spacecraft re-enter the atmosphere regularly and break up into pieces, said Ivan Oelrich, vice president for strategic security programs at the Federation of American Scientists. He said, "One could be forgiven for asking if this is just an excuse to test an anti-satellite weapon." A key issue when China shot down its defunct weather satellite was that it created an enormous amount of space debris. "All of the debris from this encounter, as carefully designed as it is, will be down at most within weeks, and most of it will be down within the first couple of orbits afterward," said Jeffrey. "There's an enormous difference to spacefaring nations in ... those two things." He and others dismissed suggestions that this was simply an attempt by the U.S. to flex its muscles, and that officials were overstating the toxic fuel threat. 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.