Australia, a staunch anti-whaling nation, has long threatened international legal action. Two years ago, it sent a ship to Antarctic waters to follow the Japanese whaling fleet and collect videos and photographs it said might be used as evidence in an international forum.
Prime Minister Kevin Rudd said Australia would prefer to use diplomatic means to persuade Japan to end its hunt.
"If that fails, then we will initiate court action before the commencement of the whaling season in November 2010," he told the Seven Network. "That's the bottom line and we're very clear to the Japanese, that's what we intend to do."
Japan hunts hundreds of mostly minke whales - which are not an endangered species
- in Antarctic waters each year under its whaling research program, an allowed exception to the International Whaling Commission's 1986 ban on commercial whaling. Whale meat not used for study is sold for consumption in Japan, which critics say is the real reason for the hunts.
Rudd's threat came on the eve of a visit to Australia by Japanese Foreign Minister Katsuya Okada. Whaling is expected to be a key topic of conversation when Okada meets with Australian Foreign Minister Stephen Smith this weekend. Japanese officials did not immediately have any comment ahead of the visit.
Australia has said it could argue that Japan's whaling is illegal before the International Court of Justice at The Hague or the International Tribunal for the Law of the Sea in Hamburg, Germany.
The whaling is conducted in international waters, but usually within the huge patch of ocean that is designated Australia's maritime rescue zone and that Canberra considers a whale sanctuary.
Don Rothwell, a professor of international law at the Australian National University, was commissioned by the International Fund for Animal Welfare in 2005 to explore Australia's legal options in its fight to end whaling. His report was later presented to both the Australian and New Zealand governments.
Rothwell said Australia could request the courts grant an immediate injunction requiring Japan to stop whaling. Either court would almost certainly grant the injunction, which would remain in place until the case was resolved, he said.
On Wednesday, a group of conservationists clashed with Japanese whalers in the Antarctic Ocean, the most recent in a string of increasingly aggressive confrontations between U.S.-based activist group Sea Shepherd and the whaling fleet.
