Feb. 20 (Bloomberg) -- The planned shoot-down of a broken spy satellite may have to be delayed due to poor weather, a senior U.S. defense official said.

A nine-day window opened today for a Navy ship in the Pacific Ocean to launch a Raytheon Co. missile at the 5,000- pound satellite, aiming to destroy it before it crashes to earth carrying 1,000 pounds of deadly fuel.

High waves may force the operation to be scrubbed for today, an official, speaking on condition of anonymity, told reporters at the Defense Department. Admiral Timothy Keating, head of U.S. Pacific Command, said the latest report from the scene showed ``the seas are calm enough.''

``I'm optimistic. I'm not wildly optimistic. I'm cautiously optimistic'' about the chances of success for the mission, he said. Keating said the optimal window for today would last less than six hours.

The Pentagon has determined it will have at most only one or two chances daily for the shot, lasting just seconds each time, through Feb. 29 before the satellite enters the earth's atmosphere, according to the unidentified defense official.

Three Navy ships, including the USS Lake Erie, the service's primary missile defense test vessel, are positioned to destroy the satellite at optimal orbit so that its debris would drop into the Pacific, the official said.

The Pentagon wants to fire the shot in daylight to allow maximum observation from U.S. radar, telescopes and sensors of the impact and will issue a press release giving a preliminary assessment of the result, the official said.

The satellite's fuel tank carries a highly toxic propellant called hydrazine that could disperse on landing over an area the size of about two American football fields, General James Cartwright, vice chairman of the Joint Chiefs of Staff, said last week.

Warning of Debris

Breaking the satellite into smaller pieces reduces chances that metal or the deadly hydrazine will survive the heat of re- entry. The satellite was launched in December 2006, stopped working within hours and is on course to hit Earth early next month, Cartwright said.

The Federal Aviation Administration issued an advisory today to commercial airlines and private pilots warning them to be alert through March 9 for the ``potential hazard'' of debris from the shattered satellite.

``We issued the advisory because we are not sure exactly where any debris is going to come down,'' FAA spokeswoman Laura Brown said.

This would be the first time the U.S. has used a tactical missile to destroy a spacecraft. The U.S. and other countries criticized China for destroying one of its defunct weather satellites last year in a military test.

To contact the reporter on this story: Tony Capaccio at acapaccio@bloomberg.net

Last Updated: February 20, 2008 22:02 EST