SEATTLE - A crack that could create an iceberg the size of five Hong Kongs - and destabilize one of the largest ice shelves in the Antarctic - has branched out and begun to widen more quickly, a scientist said on Wednesday.

The new fissure has turned toward the shelf's ocean edge, potentially speeding up the iceberg's process of breaking off, said Dan McGrath, a geophysicist with the US Geological Survey and a project partner with UK-based monitoring group Project Midas, which reported on the new crack on Monday.

"It's taking basically a sharp hook toward the calving front," said McGrath, using a technical term to describe the ocean side of the ice shelf.