WASHINGTON (REUTERS) - The United States (US) is sending a heavy icebreaker to help free a Russian ship and a Chinese icebreaker gripped by Antarctic ice, the Coast Guard said on Saturday.

The Polar Star is responding to a request for assistance from Australian authorities as well as from the Russian and Chinese governments, it said in a statement.

"The US Coast Guard stands ready to respond to Australia's request," Coast Guard Pacific Area Commander Vice Admiral Paul Zukunft said. "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."

A Chinese icebreaker that helped rescue 52 passengers from a Russian ship stranded in Antarctic ice found itself stuck in heavy ice on Friday.

The Snow Dragon ferried the passengers from the stranded Russian ship to an Australian icebreaker late on Thursday. It now had concerns about its own ability to move through heavy ice, the Australian Maritime Safety Authority said.

The Russian-owned research ship left New Zealand on Nov 28 to commemorate the 100th anniversary of an Antarctic journey led by Australian explorer Douglas Mawson.

It became trapped on Dec 24, 100 nautical miles east of French Antarctic station Dumont d'Urville and about 1,500 nautical miles south of Tasmania.

During their time on the ice, passengers amused themselves with movies, classes in knot tying, languages, yoga and photography, and rang in the New Year with dinner, drinks and a song their adventure.

The Polar Star is 120 metres long with a maximum speed of 18 knots. It can continuously break 1.8 metres of ice at three knots, and can break 6.4 metres of ice backing and ramming, the Coast Guard said.

The cutter is cutting short its planned stop in Sydney to help with the mission.