Royal Dutch Shell has halted its drilling in the Arctic one day after it began because sea ice is moving toward the company's drill ship off Alaska.
Shell Alaska spokesman Curtis Smith said drilling was stopped as a precautionary measure.
He said drilling will resume when the ice, which measures about 30 miles by 12 miles, has moved on.
On Sunday Shell announced that it had been more than two decades since a drill bit had touched the US Chukchi Sea floor.
Environmental groups bitterly oppose Arctic drilling, saying oil companies have not shown they can clean up a spill in ice-choked water.
The oil giant was given permission last month to begin preliminary work on an exploratory well.