SEATTLE -

The Coast Guard says its icebreaker Polar Star is no longer needed for an Antarctic rescue mission after both a Russian research ship and a Chinese icebreaker that tried to help the Russian vessel broke free of heavy pack ice.

The Coast Guard Pacific Area command center in Alameda, Calif., said yesterday it had been told by the Australian Maritime Safety Authority that both ships were free and the Polar Star's help was no longer necessary.

The Polar Star left its Seattle homeport last month on a mission to break a channel through the sea ice of McMurdo Sound to allow the resupply and refueling of the U.S. Antarctic Program's McMurdo and Amundsen-Scott South Pole stations. It was asked last Friday to help the stranded ships.

The 399-foot-long ship will now return to its original mission.

It's the Coast Guard's only active heavy polar icebreaker.