Washington - The Pentagon says bad weather at sea appears likely to put off, until at least Thursday, an attempt to shoot down the wayward U.S. spy satellite.

The attempt, which was scheduled for sometime after 8:30 Tucson time tonight, would use a Navy heat-seeking missile made by Tucson-based Raytheon Missile Systems.

Weather conditions are one of many factors that U.S. military officers are taking into account as they decide whether to proceed with the mission Wednesday or to put it off, according to a senior military officer who briefed reporters at the Pentagon.

The officer said the assumption had been that the mission would go forward Wednesday night, unless conditions are determined to be unfavorable. Earlier in the day, bad weather in the north Pacific was causing rough seas, which may be a problem for the USS Lake Erie, a cruiser armed with two SM-3 missiles.

"We don't anticipate the weather being good enough today," the officer said, adding that conditions could improve enough in the hours ahead to permit it to go forward. A final decision would be made by Defense Secretary Robert Gates.

Alluding to the high seas and strong winds, the officer added, "It has not been enough for us to say 'no'" and put the launch mission off until Thursday. But it would take improved conditions to proceed."

The Pentagon had been waiting until the space shuttle Atlantis returned to Earth before launching the missile.

"We're now into the window," the senior military officer said minutes after the shuttle landed at 9:07 a.m. EST.

He said the mission could go forward on any day until Feb. 29, when the satellite is projected to have re-entered the Earth's atmosphere, making it infeasible to attempt to hit it with the Navy missile.