New Zealand and Australia announced Wednesday they will lead a formal diplomatic protest against Japan's move to catch more than 1,000 whales in the Antarctic over the southern hemisphere summer.

At the same time, the Greenpeace environmental organization's protest ship Esperanza left Auckland in a bid to stop four Japanese boats heading for the Southern Ocean with the express aim of killing 935 minke whales, 50 fin whales and 50 humpback whales.

Tokyo claims its annual foray into Antarctic waters is a scientific research mission, but Wellington and Canberra, backed by environmentalists around the world, condemn it as ill-disguised commercial whaling designed to catch meat for Japanese shops.

The Japanese government reacted calmly Wednesday to the prospect of a diplomatic protest, saying it would work to maintain friendly ties with Australia.

Chief Cabinet Secretary Nobutaka Machimura insisted that Japan's whaling is conducted "in line with" rules of the International Whaling Commission, to which Australia also belongs, Kyodo news agency reported.

New Zealand Conservation Minister Steve Chadwick said 27 countries joined last year's diplomatic protest against Japan.

"Humpback and fin whale populations are yet to recover from decades of over-exploitation from commercial whaling," she said. "New Zealand totally rejects claims that lethal whaling is needed for scientific research."

The leader of the Greenpeace expedition, New Zealander Karli Thomas, said Esperanza's crew plans to launch inflatable rafts manned by volunteers between the whales and the Japanese boats' harpoons.

The Australian government has announced that it will send ships, including the 105-metre Oceanic Viking, a customs' service icebreaker with a civilian crew, and aircraft to monitor the Japanese fleet.

Foreign Affairs Minister Stephen Smith said Australia was formally protesting to Japan about its whale slaughter, but would not use force.

"It will be surveillance, not enforcement, or intervention," Smith told reporters in Sydney. "For the purposes of that surveillance, the customs party will not be armed."

He said the intention was to collect evidence that could be used in a legal challenge to whaling.

"All options are on the table, including utilizing the whaling convention, utilizing the endangered species convention, taking action before the International Court of Justice, and taking action before the International Tribunal of the Law of the Sea," Smith added.

Greenpeace's Thomas said the Esperanza's task was challenging because its helicopter was out of action and the hunting area covered more than 1 million square nautical miles, but she added, "We're pretty confident we can find them anyway."

The US-based Sea Shepherd Conservation Society has sent a ship to the Southern Ocean and has vowed to use whatever means necessary to thwart the whalers.