Wellington  - Fears were rising for two Japanese climbers stranded in New Zealand's Southern Alps for a week as appalling weather ruled out another attempt to airlift them to safety on Thursday.

A bag of emergency supplies, including a radio, was dropped to the climbers, who are holed up in a tent 3,700 metres up New Zealand's highest peak Mount Cook, on Wednesday but a Conservation Department spokeswoman said it was not certain they had retrieved it.

Shirley Slatter told Radio New Zealand that one of the men had looked out of the tent and waved at the helicopter but they had made no radio contact and it was not clear that they realised the bag had been dropped.

She said a storm, with thunder and lightning, driving rain and winds up to 130 kilometres an hour was strafing the mountain early Thursday morning, making a rescue attempt impossible.

"They're sitting literally at the top of New Zealand," she said. "It is not a great place to be at the moment."

Police named the men as Kiyoshi Ikenouchi, 49, a mountain guide, and Hideaki Nara, 51, both from Tokyo.

Only one of them has been seen by searching helicopters and nothing is known about the condition of the other.

Forecasters said it may be Saturday before the weather cleared enough for a helicopter to lift them off the mountain. (dpa)