The 18th round of a U.N. disarmament conference kicked off Monday in Yokohama with government representatives and researchers from 15 countries attending, including the United States and Iran.

The participants are expected to mainly discuss nuclear programs in North Korea and Iran at the three-day event, whose theme is "Alarming Nuclear Proliferation Crisis and Regional Peace and Security," government officials said.

High on the agenda will be trade in nuclear equipment and technology on the black market, a cause of proliferation, the officials said.

Japan has hosted the annual conference since 1989.