U.N. Secretary-General Antonio Guterres said Wednesday he has high hopes that a disarmament conference that started this week will lead to reaffirmation of the norm that nuclear weapons should never be used, in comments ahead of his visit to Hiroshima for the upcoming anniversary of the U.S. atomic bombing of the city.

"Those that possess nuclear weapons have a clear responsibility not to admit the possibility of any kind of nuclear confrontation," the secretary-general said in a meeting with Japanese media organizations on the sidelines of the Nuclear Non-Proliferation Treaty review conference at the U.N. headquarters. The four-week conference started Monday.

Guterres will be the first U.N. chief to attend the Hiroshima anniversary since Ban Ki Moon in 2010, with his visit coming amid threats by Russia to use nuclear weapons in its war against Ukraine.