Passengers onboard a ship stuck in ice off Antarctica were Saturday placing their hopes in the Australian icebreaker hurrying to their remote location, after a Chinese icebreaker failed to free them.
The Australian Maritime Safety Authority (AMSA), which is coordinating the rescue of the Russian passenger ship MV Akademik Shokalskiy, said the icebreaker came within six-and-a-half nautical miles of the ship but had to stop.
"The Chinese vessel unfortunately encountered some heavy ice that it's not capable of breaking through," AMSA spokeswoman Andrea Hayward-Maher told AFP. "The rescue... unfortunately has stalled."
The Russian ship, with 74 scientists, tourists and crew on board, has been trapped in ice about 100 nautical miles east of the French base Dumont d'Urville since Tuesday.
The Chinese vessel came tantalisingly close to the stranded ship but it was forced to turn back to open sea once it realised it could not break through.
Passengers are now waiting for the arrival, expected late Sunday, of Australia's Antarctic resupply ship Aurora Australis which has the highest icebreaking rating of the three vessels originally asked to respond.
It is not yet clear whether the Aurora Australis will be able to go any further than the Chinese vessel, the Snow Dragon. A third ship, the French vessel L'Astrolabe, was released from the rescue mission on Saturday.
"We all know that there's a possibility of this becoming quite a protracted sit and wait," said Andrew Peacock, a passenger onboard the Akademik Shokalskiy, speaking to AFP via satellite phone.
"I think people are just looking at that next step when that second icebreaker arrives.
"We really are just hoping that the... two powerful icebreaker ships will provide the breakage of ice that we need."
The captain of the Aurora, Murray Doyle, said his ship -- which can cut through ice up to 1.35 metres thick or reverse and ram thicker ice to break it up -- was always "option B".
"We were always going to be sent on until the end," he told a Sydney Morning Herald reporter onboard his ship, but admitted the ship was not built to take on ice thicker than three metres.
He said trying to break through ice that was too thick would be "like driving your car into a brick wall'".
Peacock said while there was an element of frustration at the turn of events, passengers had been delighted the Chinese ship had been able to get close to their remote location as quickly as it did.
"It certainly tried hard," Peacock said, adding it was still visible off the ship's starboard side when it was not snowing.
AMSA said Saturday it was "assessing options" regarding the rescue of the Russian ship which is approximately 1500 nautical miles south of the southern Australian city of Hobart.
"A helicopter-equipped Chinese-flagged vessel remains in the vicinity to assist if necessary," it said in a statement.
The Akademik Shokalskiy is carrying scientists and tourists who are following the Antarctic path of explorer Sir Douglas Mawson a century ago and Peacock, the expedition's doctor, said the work was continuing.
Some passengers were also walking near the boat, watching the Adelie penguins and ice formations which had formed around the ship in the past few days, he said.
Those onboard have been carrying out the same scientific experiments Mawson's team conducted during the 1911-1914 Australian Antarctic Expedition -- the first large-scale Australian-led scientific expedition to the frozen continent.
Several members of the team have already battled sea ice to reach the historic Mawson's Huts -- built and occupied by the 1911-1914 expedition -- which have been isolated for years by a giant iceberg.
The group, which includes Australians, New Zealanders and Britons, became stuck when unexpected weather forced their ship into heavy ice. An intense blizzard appears to have increased the build up of ice around them.
Peacock said it seemed that the ice floes had pushed up against each other to remodel the once flat landscape since they became stranded.
"Ridges have formed in the night... the ice is quite featured," he said.
"So when we get the midnight sun and the shadows thrown across... it's absolutely spectacular."
They have been onboard for three weeks and had planned to return to New Zealand by early January.
Peacock said the ship was well supplied and all passengers were comfortable.
"The beer is running low," he joked.