THE HAGUE, Netherlands — Japan launched an impassioned defense Tuesday of its harpooning of whales in the icy seas around Antarctica, insisting the hunt is legal because it gathers valuable scientific data that could pave the way to a resumption of sustainable whaling in the future.

The country is arguing a case brought by Australia to the United Nations' highest judicial organ that seeks to outlaw its annual killing of hundreds of whales in Antarctic waters.

"It is true that Japan takes and kills whales," the country's deputy foreign minister, Koji Tsuruoka, told the International Court of Justice, on the first day of arguments. "Should we be ashamed of it? Even if some people believe we should, that does not mean we are in breach of international law."

Tsuruoka implicitly accused Australia of launching the case to impose on Japan its cultural aversion to whaling rather than to right an international legal wrong.

"It falls to the court to rule on the lawfulness of the acts undertaken by states, not on their morality or their ethical value," he said. "For some people, whales are sacred animals like cows are for Hindus. Religions and cultures perceive animals in different fashions."

Under a 1946 treaty regulating whaling, nations can grant permits to kill whales for scientific research.

Lawyers for Australia argue that Japan's scientific whaling program was set up simply to sidestep a 1986 moratorium on commercial whaling. Meat from the whales ends up on plates in homes and restaurants across Japan, where the flesh is considered a delicacy.

"No other nation, before or since, has found the need to engage in lethal scientific research on anything like this scale," Australian Solicitor-General Justin Gleeson told the judges last week. Australia argues that such research can be carried out without killing whales.

But Tsuruoka said the hunt is designed to provide the International Whaling Commission with valuable data that would allow it to grant a resumption of whaling in a sustainable way, unlike the mass carnage of unregulated whaling that pushed many species of the giant marine mammals to the brink of extinction in the last century.

Lawyer Alain Pellet, representing Japan, also argued that the court does not even have jurisdiction to hear the case because Australia has expressed reservations in the past about the court's jurisdiction in maritime cases.

Geert Vons, of the Dutch arm of the Sea Shepherd conservation group that has battled Japanese whalers on the high seas for years, dismissed Japan's scientific justification for authorizing the hunting of minke, fin and humpback whales — though no humpback whales have been killed.

"How can science hold if it means the killing of these three species which are on the list of endangered species?" he said. "It does not make sense."

Hearings in The Hague are scheduled to wrap up July 16 and the 16-judge world court will take months to issue a judgment.

Australia is hoping it could come before year's end so that if judges rule to ban whaling it would be in time to prevent the Japanese fleet setting off for Antarctic waters next Southern Hemisphere summer.