Hardline anti-whaling activists are threatening to sacrifice their ship in Antarctic waters by ramming a Japanese whaler.
Captain Paul Watson, head of the Sea Shepherd Conservation Society, said his vessel, the Farley Mowat, was almost out of fuel and he was considering giving the Japanese whaler, the Nisshin Maru, a "steel enema" by ramming its slipway.
Watson said his boat, currently north of the Balleny Islands, west of the Ross Sea, was now seen as a pirate vessel, and he would rather lose it in defence of whales than to bureaucrats.
"I have spent 30 years of my life trying to protect whales. I am getting sick and tired of politicians doing nothing," he said.
He intends to take drastic action, probably in the next 24 hours, to slam his vessel into the Nisshin Maru's slipway, preventing it from hunting more whales.
"We would probably be stuck into them. They would have to go back to Tokyo with us sticking out of their rear end," he said.
"Perhaps it's time to give these cruel whalers a steel enema they will never forget."
Watson said the move could be avoided only by a pledge from the New Zealand or the Australian government to stop the "criminal operations" by the Japanese.
"Perhaps it is time for a dramatic showdown after 20 years of illegal whaling activity in the Antarctic Whale Sanctuary," a statement from Sea Shepherd said.
The Farley Mowat was rated a pirate vessel after leaving Melbourne on December 29, while the other Sea Shepherd ship, the Robert Hunter, will lose its British registration on February 19.
Meanwhile, Greenpeace anti-whaling protesters have still to find the whaling vessels.
Sara Holden, aboard their vessel the Esperanza, said they were enroute to try to locate the Japanese fleet.
About 4pm (1400 AEDT), Watson told AAP he was in a confrontation with Japanese whaler the Keiko Maru.
He said the Japanese boat appeared to have headed into an icefield in an attempt to lose the protesters.
"We will be coming up behind. Our objective is to stop them in the ice," he said.
"I think they will find that we are the more manoeuvrable ship in the ice."
Watson said the confrontation was not part of his "drastic showdown" he had planned with the main Japanese whaler, the Nisshin Maru.