Japanese ruling party lawmakers have questioned a plan to sign a defence logistics accord with Australia as the two countries are at loggerheads over Japan's annual whale hunts, an official said Tuesday.

The move comes as anti-whaling activists of the Sea Shepherd Conservation Society have been harassing a Japanese whaling fleet on its annual hunt for hundreds of the sea mammals in Antarctic waters.

Australia opposes the hunts, carried out despite a 1986 international moratorium on commercial whaling under a loophole that allows "lethal research" whaling, and has threatened international legal action against Japan.

Japan's government is considering submitting a bill to parliament on a defence pact that would allow the two countries' militaries to share food, fuel and other supplies and services in their operations overseas.

But some lawmakers of the ruling centre-left coalition called on the government to "cautiously" handle the accord when the vice defence minister, Kazuya Shimba, explained the bill to them, a defence ministry spokeswoman said.

The lawmakers argued that signing a so-called Acquisition and Cross-servicing Agreement should be reconsidered in light of the recent harassment of Japan's whaling fleet.

"According to our vice minister, one of the lawmakers said he wants the government to insist on Japan's current position," defending its right to hunt whales as part of its national heritage, the ministry spokeswoman said.

The vice minister had replied to the group of lawmakers that, although any two countries face their own particular bilateral issues, it was important "to maintain military relations of trust," she told AFP.

In the latest showdown between Japanese whalers and the activists, the environmentalists' high-tech superboat, the New Zealand-registered Ady Gil, sank in Antarctic seas in early January after a collision with the whaling fleet's security ship.

New Zealand and Australian authorities are investigating the incident, while Japan has lodged a strong protest with the Wellington government.

Both the whalers and the protesters blame each other for the crash.