Hiroshima Mayor Kazumi Matsui has called on U.N. Secretary General Antonio Guterres to take part in a peace conference to be held in Nagasaki in August.

Matsui made the request in a Monday meeting with Izumi Nakamitsu, the new U.N. undersecretary general and high representative for disarmament affairs, handing over a letter written jointly with Nagasaki Mayor Tomihisa Taue.

Matsui, president of the nongovernmental organization Mayors for Peace, said he told Nakamitsu that many citizens, including survivors of the U.S. atomic bombings of Hiroshima and Nagasaki, hope for progress in the negotiations to ban nuclear weapons.

Mayors for Peace, an organization seeking nuclear disarmament and world peace, involves about 7,300 cities in 162 countries and regions. It is scheduled to convene a general conference in Nagasaki on Aug. 7-10.

Nakamitsu, who took her new posts on May 1, was quoted as saying that the key will be how nuclear powers and non-nuclear nations can work together to make the proposed nuclear ban treaty effective. So far, major nuclear powers have refused to join the negotiations.

Matsui and Nakamitsu met on the sidelines of a meeting in Vienna of the preparatory committee for a 2020 conference to review the Nuclear Non-Proliferation Treaty.