Ice that has trapped a Russian ship with 74 people on board in Antarctica appears to be cracking up.

The cracks in the ice have raised hope for a rescue as a powerful Australian icebreaker approaches the stranded vessel.

The ice-bound ship, the Akademik Shokalskiy, left New Zealand on 28 November on a privately funded expedition to commemorate the 100th anniversary of an Antarctic journey led by Australian explorer Douglas Mawson.

It has been stuck in the ice since Christmas Eve.

Its passengers include scientists and tourists, many of them Australian, and a Russian crew.

The Australian icebreaker the Aurora Australis is expected to reach the stricken ship at about midnight.

A Chinese icebreaker could not break through the thick ice earlier, but the weather today bodes well for a rescue.

"The ice conditions seem to have improved and there appears to be some softening and some cracks appearing," said Lisa Martin of the Australian Maritime Safety Authority, which is coordinating the rescue.

Just how the rescue would be done would be worked out when the Aurora reaches the area, she said.

Those on board were in good condition and have never been in any imminent danger.

"We're primarily looking to the Aurora to get us out," ChrisTurney, an Australian professor on board the beleaguered ship who is leading the expedition, wrote in an email to Reuters.

"Hopefully there are some breaks developing in the surface from the weaker winds and sun during today."

The ship is stuck about 100 miles east of the French Antarctic station Dumont D'Urville and about 1,500 miles south of Hobart in Tasmania.

The Aurora is the third icebreaker seconded by the Australian maritime rescue agency to try to reach the ship.

The Chinese icebreaker, the Snow Dragon, is on standby at the edge of the ice and within sight of the trapped ship. It has a helicopter on board, which could be used in the rescue.

A French icebreaker has also tried to help.