Sydney (AFP) - US icebreaker Polar Star was Sunday set to sail for the Antarctic to assist a Russian vessel trapped in heavy ice and a Chinese ship which went to its aid, officials said.
The Australian Maritime Safety Authority said the US Coast Guard had accepted its request to help the stranded Russian ship Akademik Shokalskiy and Chinese icebreaker Xue Long, which itself became trapped after using its helicopter to ferry dozens of passengers to the safety of an Australian ship.
The Polar Star, which is on a mission to clear a navigable channel to resupply McMurdo Station research base, will depart from Sydney Sunday after taking on supplies, it said in a statement.
The 122-metre (399-foot) ship is capable of continuously breaking ice up to 1.8 metres (six feet) while travelling at three knots and can break ice more than six metres thick by ramming.
It is expected to take seven days to reach Commonwealth Bay where the two ships are trapped in ice.
"Our highest priority is safety of life at sea, which is why we are assisting in breaking a navigational path for both of these vessels," Vice Admiral Paul Zukunft, US Coast Guard Pacific area commander, said in a statement.
The Xue Long, or Snow Dragon, came tantalisingly close to cutting through heavy ice to reach the Shokalskiy a week ago but had to abandon its attempt once it realised it could not break through.
Chinese news agency Xinhua, which has reporters onboard the Xue Long, said the ship's passage had been blocked since Friday by a drifting, one-kilometre long iceberg.
The Shokalskiy remains stuck in ice 100 nautical miles from the French Antarctic base of Dumont d'Urville with 22 crew on board.
The 22 scientists, 26 paying passengers and four journalists on board the Shokalskiy who were helicoptered off the ship on Thursday are now on the Australian Antarctic supply ship Aurora Australis.
The Aurora Australis is now set to deliver supplies to Australia's Antarctic base Casey before heading to the Australian city of Hobart.
Australian authorities have said that any inquiry into how the Shokalskiy came to be stranded would have to be conducted by Russian authorities but have acknowledged that the incident could impact guidelines for polar expeditions.
The rescue mission, which also initially involved the French ship the Astrolabe, has also impacted some Antarctic research programmes, according to Yves Frenot, director of the French Polar Institute.
The rescue mission forced French scientists to scrap a two-week oceanographic campaign using the Astrolabe, he said.
"But we are relatively lucky. The Chinese have had to cancel all their scientific programme, and my counterpart in Australia is spitting tacks with anger, because their entire summer has been wiped out," he said.
The Aurora was forced to suspend its resupply of the Australian base to rush to the aid of the Shokalskiy, but authorities said it was not yet known what impact the incident would have on scientific programmes.
The trip on the Akademik Shokalskiy was aimed at emulating a 1911-1914 expedition by the Australian explorer Sir Douglas Mawson.
The scientists onboard, assisted by the passengers, were repeating century-old measurements to discover the environmental changes taking place in the frozen southern region.