Japan will draw up a plan to help the United States and Canada with debris along their Pacific coasts, as it looks to pay back support received after last year's tsunami, officials said Wednesday.

Tokyo is aiming to offer help, possibly in the form of payment, as a way of showing its gratitude for the outpouring of sympathy in the days and weeks after the monster waves devastated the country's northeast coast in March 2011.

"Although Japan is not obliged to retrieve debris on the North American side of the Pacific, we can't say we will do nothing about it as we received enormous support from the United States and other countries after the disaster," an official at the Cabinet Office told AFP.

"In addition to the cooperation we are already engaged in through NGO activities and through providing information on debris, we are studying measures, including the option of paying for the clean-up," he said.

"We hope to decide what measures Japan will take before the bulk of the debris reaches North America's Pacific coasts" in autumn, he said.

Prime Minister Yoshihiko Noda told the US that Japan would take measures to help retrieve debris when he visited Washington in April, the official added.

Various items from the massive tsunami that killed around 19,000 people have begun washing up on the US and Canadian west coast, and experts predict a surge of flotsam in the coming months.

In June, a huge floating dock was found on an Oregon beach having travelled across the Pacific from the port of Misawa in Japan's northern Aomori prefecture. Other items have included a motorcycle and a fishing boat, which was eventually scuttled by coastguards.

A football found in Alaska was returned to a Japanese teenager who lost his house and all its contents when the waves of last year swept over his hometown of Rikuzentakata.