As of a few weeks ago:
[Gordon Johndroe, a spokesman for the National Security Council] would not comment on whether it is possible for the satellite to be perhaps shot down by a missile. He said it would be inappropriate to discuss any specifics at this time.
Now, apparently, it is appropriate, and plans are being made to shoot it down with a Standard Missile 3:
U.S. will try to shoot down disabled, toxic spy satellite
By Aamer Madhani | Washington Bureau
February 15, 2008
WASHINGTON - The Navy is preparing to shoot a faltering U.S. spy satellite out of the sky in the next two weeks using a tactical missile that was manufactured as a defensive weapon to head off enemy aircraft, the Pentagon announced on Thursday.
While it's not uncommon for space junk to fall out of the sky, military officials said they are concerned in this case because much of the 1,000 pounds of frozen rocket fuel called hydrazine on the spacecraft could survive the descent and pose health risks, such as damage to skin and lung tissue, if it lands in a populated area.
Marine Gen. James Cartwright, vice chairman of the Joint Chiefs of Staff, and James Jeffrey, the deputy national security adviser, said the Navy's window of opportunity to strike the satellite before it enters the Earth's atmosphere begins in the next three or four days.
If the satellite is not intercepted, it is expected to enter the atmosphere in late February or early March.
"This has no aerodynamic properties," Cartwright said of the satellite. "Once it hits the atmosphere, it tumbles, it breaks apart. It is very unpredictable and next to impossible to engage. So what we're trying to do here is catch it just prior to the last minute ... outside the atmosphere."
Three Navy ships will deploy in the Pacific Ocean to launch the missile. Cartwright declined to specify an exact location beyond stating it would be in the Northern Hemisphere. At the time of the launch, officials said the satellite would be about 150 miles above the Earth.
Software for the Strategic Missile 3, designed as an anti-aircraft system, is being modified to adjust for the bus-size satellite. Military officials have "high confidence" that the missile will strike the satellite and puncture its fuel tank.
If the first attempt fails, officials would have to decide whether to take another shot, but it could be "next to impossible" to strike on a subsequent attempt, Cartwright said. [emphasis added]