Washington ? A missile launched from a Navy cruiser soared 130 miles above the Pacific and smashed a dying and potentially deadly U.S. spy satellite Wednesday, the Pentagon said. Two defense officials said it apparently achieved the main aim of destroying an onboard tank of toxic fuel.

Officials had expressed cautious optimism that the missile would hit the satellite, which was the size of a school bus. But they were less certain of hitting the smaller, more worrisome fuel tank, whose contents posed what Bush administration officials deemed a potential health hazard to humans if it landed intact.

In a statement announcing that the attack on the satellite, the Pentagon said, “Confirmation that the fuel tank has been fragmented should be available within 24 hours.” It made no mention of early indications, but two defense officials close to the situation said later that it appeared the fuel tank was hit. One said observers saw what appeared to be an explosion, indicating that the tank was hit.

Because the satellite was orbiting at a relatively low altitude at the time it was hit by the missile, debris will begin to re-enter the Earth’s atmosphere immediately, the Pentagon statement said.

“Nearly all of the debris will burn up on re-entry within 24-48 hours and the remaining debris should re-enter within 40 days,” it said.

The USS Lake Erie, armed with an SM-3 missile designed to knock down incoming missiles – not orbiting satellites – launched the attack at 9:26 p.m. CST, according to the Pentagon. It hit the satellite about three minutes later as the spacecraft traveled in polar orbit at more than 17,000 mph.

The Lake Erie and two other Navy warships, as well as the SM-3 missile and other components, were modified in a hurry-up project headed by the Navy in January. The missile alone cost nearly $10 million, and officials estimated that the total cost of the project was at least $30 million.

The launch of the Navy missile amounted to an unprecedented use of components of the Pentagon’s missile defense system, designed to shoot down hostile ballistic missiles in flight – not kill satellites.

The operation was so extraordinary, with such intense international publicity and political ramifications, that Defense Secretary Robert Gates – not a military commander – made the decision to pull the trigger.

Gates had arrived in Hawaii a few hours before the missile was launched. He was there to begin a round-the-world trip, not to monitor the missile operation. His press secretary, Geoff Morrell, told reporters traveling with Gates that the defense chief gave the go-ahead at 12:40 p.m. CST while en route from Washington.

Morrell said Gates had a conference call during the flight with Air Force Gen. Kevin Chilton, head of Strategic Command, and Marine Gen. James Cartwright, vice chairman of the Joint Chiefs of Staff. They told him that “the conditions were ripe for an attempt, and that is when the secretary gave the go-ahead to take the shot, and wished them good luck,” Morrell said.

At 9:35 p.m. CST, Gates spoke to both generals again and “was informed that the mission was a success, that the missile had intercepted the decaying satellite, and the secretary was obviously very pleased to learn that,” Morrell said.

The government organized hazardous materials teams, under the code name “Burnt Frost,” to be flown to the site of any dangerous or otherwise sensitive debris that might land in the U.S. or elsewhere.

President Bush gave his approval last week to attempt the satellite shootdown on grounds that it was worth trying to destroy the toxic fuel on board the satellite before it could land in a populated area.

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