Iranian President Mahmoud Ahmadinejad stressed to visiting former Japanese premier Yukio Hatoyama on Sunday that Tehran opposes nuclear weapons, his official website reported.
"The Islamic Republic of Iran is fundamentally opposed to the atomic bomb and weapons of mass destruction," Ahmadinejad told Hatoyama.
"Iran and Japan can exert a common effort to create a world without atomic weapons ... Difficult but humanitarian efforts will win in the end."
Japan is the only country ever to have suffered a nuclear attack, its cities of Hiroshima and Nagasaki being targeted by the United States at the end of World War II.
Hatoyama's presence in Iran was an issue of contention in Japan, after Japanese Foreign Minister Koichiro Genba reportedly requested he not make the trip.
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Prime Minister Yoshihiko Nodahe has also expressed concerns over Hatoyama's visit, fearing it could undermine the Japanese government's efforts for international coordination, Japanese media reported.
The visit came at a tense time, with Iran facing off against much of the West over its nuclear programme.
The United States and its allies fear Iran is seeking nuclear weapons capability, something Tehran denies.
Talks between Iran and the five permanent UN Security Council members and Germany are due to be held starting Friday, in a country yet to be agreed.
Hatoyama was quoted as telling Ahmadinejad: "International trust-building and respecting regulations are important part of the world community which should be seriously pursued."
Ahmadinejad said Iran was "ready for negotiations" and had unspecified "practical suggestions for the upcoming meeting."