Part of East Antarctica is more vulnerable than expected to a thaw that could trigger an unstoppable slide of ice into the ocean and raise world sea levels for thousands of years, a new study showed.

The Wilkes Basin in East Antarctica, stretching more than 1,000 km inland, has enough ice to raise sea levels by 3 to 4 metres if it were to melt as an effect of global warming, the report said.

The Wilkes is vulnerable because it is held in place by a small rim of ice, resting on bedrock below sea level by the coast of the frozen continent. That "ice plug" might melt away in coming centuries if ocean waters warm up.

"East Antarctica's Wilkes Basin is like a bottle on a slant. Once uncorked, it empties out," Matthias Mengel of the Potsdam Institute for Climate Impact Research, lead author of the study in the journal Nature Climate Change, said in a statement.

Co-author Anders Levermann, also at Potsdam in Germany, told Reuters the main finding was that the ice flow would be irreversible, if set in motion. He said there was still time to limit warming to levels to keep the ice plug in place.