CHRISTCHURCH, New Zealand (AP) _ A U.S. flight to rescue a South Pole research station doctor who has a lump in her breast was delayed today by poor visibility in Antarctica.

High winds and swirling snow kept two Air National Guard Hercules LC-130 cargo planes from taking off for McMurdo, on the northern coast of Antarctica. The mission was rescheduled for Wednesday.

When the planes arrive in McMurdo, they must wait until the temperature at the Amundsen-Scott South Pole Station rises above minus 58 degrees before flying there to rescue Dr. Jerri Nielsen.

A replacement doctor for the station and a team of medics to treat Nielsen are on one of the two planes, both of which are fitted with skis to allow them to land on the ice at Amundsen-Scott base.

Nielsen, 44, is the only physician among 41 researchers at the Amundsen-Scott base. She discovered the lump in her breast earlier this year, but could not be rescued because of the harsh polar weather.

A daring July flight airdropped medical supplies to Nielsen, and she is believed to have been treating herself with chemotherapy since then.

Air National Guard Capt. Chris Sander said the plane would be grounded for at least a day because of the weather.

He said they now hope to leave early Wednesday, but that departure is also in doubt because weather forecasts for Antarctica predicted low clouds.

The flight could be delayed until Oct. 22, when the first flights of the summer were due to go to McMurdo.

``But we're going to do everything that we can to get in there as soon as possible,'' Sander said.