Officials in Japan and Australia are working to resolve a row over two protesters detained on a Japanese whaling vessel in the Southern Ocean.
The Japanese proposed conditions for the release (Image: ICR)
Japanese crewmen took the protesters, from the radical Sea Shepherd group, into custody on Tuesday after they tried to board their vessel.
The whalers say they are trying to return the two men but accuse Sea Shepherd of not co-operating.
Sea Shepherd say Japanese conditions for the handover are unacceptable.
The Sea Shepherd crew have been pursuing the Japanese fleet with the aim of using direct action to disrupt the hunt.
The whalers say Sea Shepherd activists have injured crew members in the past and accuse them of dangerous harassment.
The two men, Brighton-born Giles Lane, who lives in Leeds in Britain, and Australian Benjamin Potts, boarded the Yushin Maru 2 vessel on Tuesday to deliver a petition.
Sea Shepherd say they were assaulted and tied to the radar mast by the Japanese crew.
But whaling officials said the pair had not been harmed, describing the claims as "completely untrue".
They said the men had illegally boarded the vessel after trying to damage its propeller and throwing bottles of acid.
A spokesman for Japan's Ministry of Foreign Affairs, Tomohiko Taniguchi, said that there was a strong desire on the Japanese side to return the two men.
Officials had contacted Sea Shepherd but received no response, he said.
A condition of the handover was that Sea Shepherd agreed to remain 10 miles from Japanese vessels.
"If Sea Shepherd is not willing to do what the Japanese side wants them to do, I'm afraid it will take more time," he said.
Calling the two men hostages was incorrect, he added. "The two crew members were intentionally left behind on board."
Sea Shepherd, meanwhile, described a conditional release as unacceptable.
Australian Foreign Minister Stephen Smith said he expected the men to be returned "in a safe and secure condition".
"And the Japanese government also wants that to occur," he added. "What is now needed is the co-operation of the two vessels involved."
The Japanese fleet plans to kill about 900 minke whales and 50 fin whales by mid-April as part of what it describes as a scientific research programme.
But other nations and environment groups say the research goals could be achieved using non-lethal methods and call the programme a front for commercial whaling.
TRACKING JAPANESE WHALERS
November 2007: Japanese fleet of six whaling ships sets sail
31 December: MV Esperanza carrying Greenpeace campaigners enters Antarctic waters on trail of Japanese fleet. MV Steve Irwin carrying rival Sea Shepherd Conservation Group also heads towards whaling fleet
9 January: Australian ship Oceanic Viking leaves Perth on whaling surveillance mission
15 January: Two Britons held by Japanese after boarding Yushin Maru No 2 to deliver protest letter