The US Navy may make its first attempt to shoot down an errant spy satellite loaded with toxic fuel in an area of the Pacific Ocean west of Hawaii.
A notice to mariners broadcast by the National Geospatial Intelligence Agency has warned of hazardous operations in the area between 0230 and 0500 GMT on Thursday.
The Federal Aviation Administration issued a similar notice to pilots.
Officials say the notices are intended to clear the area of shipping and air traffic during what could be an initial attempt to down the bus-sized satellite from a U.S. Navy ship in the Pacific.
A Pentagon spokesman says no decision about when to attempt the shootdown has yet been made.