The U.S. representative to the International Whaling Commission, Monica Medina, discussed revoking the U.S.-based conservation group's tax exempt status during a meeting with senior officials from the Fisheries Agency of Japan in November 2009, according to the documents released by WikiLeaks on Monday.
Sea Shepherd Conservation Society's yearly protest campaigns - which chase Japan's whaling fleet in boats trying to disrupt the hunt by fouling fishing lines and throwing rancid butter at whalers - have drawn high-profile donors and volunteers, and spawned the popular Animal Planet series "Whale Wars." In Japan, the harassment is seen by some as foreign interference in national affairs, making politicians wary of getting involved.
Action against Sea Shepherd would be a "major element" in achieving success at international negotiations on the number of whales killed each year, the cables cite the director general of Japan's fisheries agency, Katsuhiro Machida, as saying.
Referring to Sea Shepherd, Medina said "she believes the USG (U.S. government) can demonstrate the group does not deserve tax exempt status based on their aggressive and harmful actions," according the cables.
Paul Watson, founder of Sea Shepherd, said Japan has previously pressured foreign governments to take action against the group, such as revoking the registration of its ships. He said the organization had last been audited about two years ago, which is before the exchanges detailed in the cables.
"We have had our tax status since 1981, and we have done nothing different since then to cause the IRS (Internal Revenue Service) to change that," he told The Associated Press by telephone from his ship.
The diplomatic cables, posted on WikiLeaks' secret-sharing website early Monday but dated Jan. 1, show Japanese officials repeatedly told U.S. counterparts the group's actions were making whaling a political issue and hurting any chance of a compromise on the numbers of whales killed each year.
Sea Shepherd vessels are currently chasing Japan's whaling fleet in the Antarctic Ocean in the hopes of interrupting its hunt, which kills up to 1,000 whales annually and typically lasts from December to February.
Japan hunts whales under the research exemption to a 1986 worldwide ban on commercial hunts. Critics say there is no reason to kill the animals, and the research program amounts to commercial whaling in disguise because surplus meat from the hunt is sold domestically.
Protest ships harass the whaling fleet, and clashes between the sides often take place. On Saturday, Watson said that whalers had shot water cannons at anti-whaling activists nearby.
Last January, a Sea Shepherd boat was sunk after its bow was sheared off in a collision with a whaling vessel and a New Zealand protestor was later arrested after he boarded a Japanese whaling ship. He was taken to Tokyo and later deported.
The cables are dated before an International Whaling Commission meeting last year that was seen as a major chance to end a decades long stalemate. They show the U.S. worked with Japan in late 2009 to reach a deal on the issue, calling it an "irritant" in international relations.
The meeting ended without a major agreement.
"Action on the SSCS (Sea Shepherd Conservation Society) would be a major element for Japan in the success of the overall negotiations," a Japanese official said, according to one cable.
Watson said Monday that his group was against anything less than a complete stop to Japan's whaling program in Antarctica. The activists hope to block whaling activities for the Japanese fleet so it incurs deep financial losses.
"I don't think a solution is going to come through politics, it's going to come through economics," Watson told The Associated Press by telephone from his ship while pursuing the Japanese fleet.