It is the first time Tokyo has backed down over one of its whaling expeditions, which have been a longstanding strain in relations with its Western allies.

It also marks a coup for Australia's new left-leaning Prime Minister Kevin Rudd, who has stepped up the pressure on Japan since taking office this month, including ordering a patrol ship and planes to track the whalers.

Japan had planned to harpoon 50 humpback whales on its current expedition, the first time since the 1960s that Tokyo would have hunted the species, which are major attractions for Australian whale-watchers.

"Japan will not hunt humpback whales," chief government spokesman Nobutaka Machimura told a news conference.

"It's true that Australia expressed quite a strong opinion to Japan on this," he said. "As a result, I hope that this will lead to better relations with Australia."

But he vowed the fleet en route to the Antarctic Ocean would go ahead with its hunt of nearly 1,000 other whales saying Australia and Japan had basic cultural differences on the issue.

"Australians consider whales to be very affectionate, something I can't really relate to. But apparently they give names to every whale and there's quite strong public sentiment," Machimura said.

Australian Foreign Minister Stephen Smith welcomed the move but called for Japan to end all whaling and vowed to press ahead with plans to monitor the hunt.

"The Australian government strongly believes that there is no credible justification for the hunting of any whales," Smith said through a spokesman, as quoted by the Australian Associated Press.

Rudd's Labor Party had accused the conservative government of his predecessor John Howard of being too soft on Japan out of consideration for economic ties.

Machimura denied Japan was bowing to Australian pressure and said it was "suspending" the hunt of humpback whales for one to two years after talks with the International Whaling Commission (IWC) chair, the American William Hogarth.

Machimura said the suspension was part of Japan's efforts to "normalise" the IWC -- Tokyo's expression for moving the 78-nation body back to its original role of managing whale hunting.

"This is a very emotional issue, but Japan insofar as possible would like to conduct its scientific research and have cool-headed discussions," Machimura said.

US ambassador to Japan Thomas Schieffer had earlier said that Japan agreed to stand down during diplomatic negotiations involving Washington, which also opposes whaling.

Japan carries out the hunt using a loophole in a 1986 IWC moratorium on commercial whaling that allows "lethal research" on the giant mammals. Only Norway and Iceland defy the moratorium outright.

Environmental movement Greenpeace and the militant splinter group Sea Shepherd have each sent a ship to Antarctic waters to try to disrupt Japan's whaling.

Humpback whales, protected under a 1966 worldwide moratorium after years of overhunting, are renowned for their complex songs and acrobatic displays.

The humpbacks' slow progression along Australia's coast to breed has turned into a major tourist attraction, bringing 1.5 million whale watchers a year.

In Japan, the government's U-turn was welcomed by environmentalists who have fought a long and lonely battle against whaling.

"This proves that international pressure can work," said Junichi Sato, who heads the anti-whaling campaign for Greenpeace Japan.

"The decision also reflects the fact that Japanese people actually don't eat whale meat a lot. Many Japanese wonder why Japan has to go all the way to Antarctic Ocean to hunt whales," Sato said.

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