The Australian government has said it plans to establish the world's biggest marine protection zone to safeguard a huge swathe of the Coral Sea, a biodiversity hotspot brimming with life.

US President Barack Obama was due in Australia Wednesday on a twice-postponed mission to update a 60-year-old security alliance for a new century marked by the rise of China.

Rescuers were racing against the clock Monday to save two huge sperm whales, the Parks and Wildlife Service said.