Echoing a call made earlier by U.S. President Barack Obama, Mayor Tomihisa Taue said some progress has been made on eliminating nuclear weapons but more efforts were required to reach the goal.
"We, as human beings, now have two paths before us," Taue said in a speech delivered after 11:02 am, the time when a plutonium bomb dropped by a US warplane flattened the southwestern Japanese city on Aug 9, 1945.
"While one can lead us to 'a world without nuclear weapons,' the other will carry us toward annihilation," Kyodo news agency quoted Taue as saying in his speech at the memorial ceremony at Nagasaki Peace Park.
In April, Obama said in Prague that the United States will seek a world without nuclear weapons, creating a wave of optimism among those who are petitioning for the abolishment of nuclear arms across the world.
He urged the international community to make North Korea destroy its nuclear arsenal and said the five major nuclear powers -- Britain, China, France, Russia and the United States -- must "fulfill their responsibility to reduce nuclear arms."
"President Obama's speech was a watershed event, in that the United States, a superpower possessing nuclear weapons, finally took a step towards the elimination of nuclear armaments," Taue said, adding that people in Nagasaki are circulating petitions urging the U.S. leader to visit the city , which was devastated by the 1945 bombing.
Japan, he said must take a leading role in disseminating around the world the "ideals of peace and renunciation of war" as stipulated in its Constitution, as the only nation to have suffered nuclear bombings.
The mayor also urged the Japanese government to legislate its three non-nuclear principles of not producing, possessing or allowing nuclear weapons on Japanese territory, and work on creating a nuclear weapon-free zone in the Northeast Asian region including North Korea.
A moment of silence was observed at 11:02 a.m., the time when a US bomber dropped an atomic bomb on the city. The bombing occurred three days after the first one was dropped on Hiroshima, which killed some 140,000 people.
Japanese Prime Minister Taro Aso, who attended the ceremony, pledged to stick to Japan's three non-nuclear principles.
The ceremony was attended by dignitaries and representatives from 29 countries.
Japan surrendered on August 15, 1945, six days after the second atomic bomb turned Nagasaki into a silent ruin, bringing an end to World War II.
