Conservation Minister Chris Carter brushed aside a demand from the Green Party to send a navy frigate to monitor the escalating confrontation, saying the navy has no legal authority in international waters.

"At this point, it is my view it would not serve any purpose to send the frigate. In fact, it might even inflame the situation further," Carter told Radio New Zealand.

He said New Zealand aircraft had been monitoring the confrontation between the fleet of six Japanese whaling ships and vessels from global environmental watchdog Greenpeace and the Sea Shepherd Conservation Society.

The air force's main mission is to look for illegal fishing activities in the southern waters, but they had also been instructed to monitor the Japanese whaling activity and the protests, the minister noted.

The confrontation, which began three weeks ago, intensified on Monday when the Sea Shepherd ship Farley Mowat sideswiped one of the whaling ships. The organisation, headed by former Greenpeace activist Paul Watson, threatened Tuesday to ram the Japanese fleet.

Greenpeace has distanced itself from any violent tactics in the anti-whaling protest, and blamed the Japanese for a collision on Sunday between its Arctic Sunrise vessel and the Japanese factory ship Nisshin Maru.

Japan maintains Greenpeace was responsible and Australian reports have quoted Japan's Fisheries Agency as saying it was considering asking for armed police aircraft to protect its fleet.

The International Whaling Commission imposed a moratorium on commercial whaling in 1986 but Japan has continued hunting for what it calls scientific research -- a claim rejected by critics.

Despite international protests, Japan has this year more than doubled its planned catch of minke whales to 935 and added 10 endangered fin whales, with plans to eventually lift the number to 50, along with 50 rare humpback whales.

"Japan is under enormous diplomatic pressure internationally over this issue," Carter said.

"The Japanese are getting acutely embarrassed by these images of bleeding and dying whales being dragged on board their boats."

All rights reserved. � 2005 Agence France-Presse. Sections of the information displayed on this page (dispatches, photographs, logos) are protected by intellectual property rights owned by Agence France-Presse. As a consequence, you may not copy, reproduce, modify, transmit, publish, display or in any way commercially exploit any of the content of this section without the prior written consent of Agence France-Presse.