Japan said on Wednesday it was very cautious about any nuclear cooperation with India and urged New Delhi to make a full accounting of its landmark atomic deal with the United States.
Japan said it could help India with its vast and growing energy needs but said the country, one of the world's top polluters and a nuclear-armed state, should take part in future efforts to fight climate change.
"As main emitters of greenhouse gases, we want India to join in a new framework" after the Kyoto Protocol expires at the end of 2012, Japanese foreign ministry spokesman Mitsuo Sakaba said.
India has signed and ratified Kyoto, currently the main international agreement aimed at reducing greenhouse gas emissions, but is not one of the countries that has to make targeted emission cuts.
New Delhi has not signed the nuclear Non-Proliferation Treaty.
But even with cooperation on the environment, Japan was hesitant about any new nuclear developments in India, even for peaceful purposes.
"Inevitably from the Japanese viewpoint, we should take a very careful position," Sakaba said in Manila on the sidelines of an Asian security summit.
"The nuclear issue is a very sensitive issue for Japan because of, needless to say, the Japanese experience at Hiroshima and Nagasaki. So we are very much concerned with any new nuclear power."
He said Japan wanted details about India's new nuclear cooperation deal with the United States, and that Japanese Prime Minister Shinzo Abe would raise the issue when he visited India later this month.