Taiji dolphins: Gwyneth Paltrow, Sean Penn and Jennifer Hudson send letter condemning hunt to President Obama

Hollywood stars and activists are urging the President to negotiate the end of the practice as part of a trade agreement with Japan.

Gwyneth Paltrow poses in the winners room at the British Fashion Awards 2013 in London. She is among the celebrities and activists to sign a letter to President Obama against dolphin hunts in Japan. (Stuart C. Wilson/Getty Images)

American activists and celebrities including Sean Penn and Gwyneth Paltrow, are urging US President Barack Obama not to sign an international trade agreement with Japan until the country bans the slaughter of dolphins.

Among those who have joined Penn and Paltrow to sign the letter written by hip-hop producer Russell Simmons, are Susan Sarandon, Jennifer Hudson, Charlize Theron, and TV personalities Ellen DeGeneres and William Shatner.

Mr Simmons claims that more than 600 dolphins have been slaughtered since the hunting season began in the fishing town of Taiji, on 1 September last year.

Anti-hunt activists have also reported that dozens of fishermen helped to herd about 250 dolphins into a cove one day in January.

Of those, about 40 were eventually killed for their meat. At least 50 others were kept alive for sale to aquariums and others, while the rest were released.

Warning: graphic content. Japanese fishermen round up and kill dolphins in the now infamous Taji cove

The 2009 Academy Award-winning documentary The Cove raised awareness and sparked protests against the annual hunt and ensuing slaughter in the town.

Japanese law currently allows a hunting season for dolphins, something that fishermen defend as a tradition.

The letter, dated Wednesday 5 Febraury, asks for the US ambassador to Japan, Caroline Kennedy, to persuade President Obama not to sign the Trans-Pacific Partnership (TPP) until Japan halts the practice.

The TPP is being negotiated by 12 nations that account for about 40 per cent of global GDP.

Ms Kennedy recently tweeted that she was deeply concerned by the tradition. Following the post, a US State Derparment spokeswoman said that the US was "concerned with both the sustainability and the humaneness of the Japanese dolphin hunts."

An member of the 'Taiji Dolphin Action Group' is curled up on a sheet depicting blood on the Japanese flag, during a protest against the killing of dolphins.

Mr Simmons' stressed that the signatories do not oppose the TPP, but want to see the dolphin hunts become a key factor in negotiations.

The letter said that corporations have spent the past two years crafting language in the TPP "to serve their interests."

"Should human compassion not be afforded the same privilege as business interests?" the letter asked.

It added: "The world is looking to you, Ambassador Kennedy, and to our government to send a clear message to Japan that this atrocity must be banned now."