The ships Arctic Sunrise and Esperanza will prepare to leave the region for Cape Town, the group said in a statement.

"Logistically we cannot remain in the Southern Ocean any longer," expedition leader Shane Rattenbury said.

"For a month now we have dogged, delayed and disrupted the whaling fleet in the Southern Ocean whale sanctuary, and have no doubt that they have fallen far behind in their bid to slaughter 935 minke whales and 10 endangered fin whales.

"It is our hope that this struggle will inspire people to help us defend whales, so that it goes down in history as the last time the peaceful silence in the sanctuary is broken by the sound of a grenade-tipped harpoon," it said.

The protests captured worldwide attention when Arctic Sunrise collided with a Japanese factory ship earlier this month. Last week an activist was knocked from an inflatable raft into the icy waters by the rope of a harpoon.

Greenpeace said it would now shift the focus on its campaign from the high seas to supermarket shelves by encouraging consumers not to buy products from companies with links to whaling.

"We're asking consumers to be aware of who funds the whale hunters, and to let them know that whaling is bad for business," chief executive officer Steve Shallhorn said.

The International Whaling Commission imposed a moratorium on commercial whaling in 1986 but Japan has continued hunting for what it calls scientific research -- a claim rejected by critics.

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