Nagasaki, Japan ? The mayor of Nagasaki, the second of the only two cities attacked with an atomic bomb, marked the 61st anniversary of the bombing Wednesday by criticizing the world’s nuclear powers for their stalled efforts to disarm.

Mayor Itcho Ito criticized those countries for not working earnestly for atomic disarmament. He spoke at a memorial service attended by about 4,800 survivors, officials and guests at Peace Memorial Park, just a few hundred yards from the center of the blast at the end of World War II.

Ito said the Nuclear Non-Proliferation Treaty, the international pact to prevent the spread of nuclear weapons, was “on the verge of collapsing.”

“The U.S. is acquiescing in India’s nuclear development and is in the process of building up a system for nuclear technology cooperation,” he said.

Ito said North Korea, which claims to possess nuclear weapons, is threatening the peace and stability of Japan, which is a participant in stalled six-nation talks on curbing North Korea’s atomic program.

On Aug. 6, 1945, the U.S. bomber Enola Gay dropped the “Little Boy” bomb on Hiroshima, killing at least 140,000 people in the world’s first atomic attack. Three days later, the B-29 Bock’s Car dropped a bomb dubbed “Fat Man” on Nagasaki, with estimates of the immediate death toll ranging from 60,000 to 80,000.

Japan, whose military had sought to create an empire across Asia and attacked the United States, surrendered Aug. 15, 1945, ending the war.