The federal Energy Department on Tuesday delayed the arrival of ships carrying radioactive waste from Europe, giving South Carolina more time to try to block the shipment in court.
The two ships early Tuesday were several miles off the North Carolina coast.
They contain 153 spent fuel rods from research reactors in Austria, Denmark, the Netherlands and Sweden.
The shipment is part of a U.S. effort to keep weapons-grade uranium out of the wrong hands.
The materiel was to come through Sunny Point Military Ocean Terminal in Brunswick County, N.C., then be shipped to the Savannah River Site weapons plant near Aiken, S.C., for storage.
Last week, a three-judge panel of the U.S. 4th Circuit Court of Appeals threw out a lower court ruling blocking the shipment.
The state contends that the Energy Department used negotiations to delay a lawsuit, then allowed the ships to sail.
As a result, the department now improperly claims the matter is an emergency, the appeal says.
State Atty. Gen. Travis Medlock said papers have already been sent to the U.S. Supreme Court to take the case there in case the 4th Circuit rejects the appeal.
"We will . . . use all means at our disposal to keep South Carolina from becoming the dumping ground for the world," Medlock said Tuesday.
The Energy Department has encouraged reactor operators around the world to stop using highly enriched uranium fuel and move to a type of uranium that cannot be easily converted to weapons use.
The federal government promised to take back all the spent fuel it sold to operators of foreign reactors.
The department wants to import a total of 409 fuel elements in the next six months and 10,000 to 15,000 during the next 10 to 15 years.