The Australian government was warned Tuesday against sending a warship to confront the Japanese whaling fleet expected this week in the Southern Ocean.

The Labor Party that took power after last month's general election has pledged to stop whaling and Prime Minister Kevin Rudd is mulling options for when the whaling season begins.

The opposition Liberal Party, which in office had limited action to diplomatic protests, has urged Rudd not to send in the navy for fear that would provoke an equivalent action by the Japanese.

The whaling fleet intends catching 935 of the smaller minke whales, 50 fin whales and 50 humpback whales on the pretext of using the carcases for research. The whale meat is sold in supermarkets.

Rudd hasn't ruled out sending in the navy but is more likely to deploy the Oceanic Viking, a customs vessel with a civilian crew.

The 105-metre vessel, which has been used to chase and impound foreign vessels poaching fish in Australian waters, is armed with large-calibre machine guns. It also has sophisticated video equipment that could be used to gather evidence for any international legal challenge against the slaughter.

International conservation agency Greenpeace said it would welcome the deployment of the Oceanic Viking.

Greenpeace's Karli Thomas said: "The more scrutiny that we can have on the Japanese whaling operation the better. There's been a very high level of international condemnation of the hunt and they're only just reaching the Southern Ocean now."

Rudd has promised a tougher stance on Japanese whaling but is unlikely to deploy navy ships. "I'm fully aware of the depth and strength of our bilateral diplomatic relationship with Japan," Rudd said.