"As the only nation in the world to have suffered a wartime nuclear attack, I have renewed my resolve to play a leading role in pursuing a world without nuclear weapons and maintain the three non-nuclear principles," Abe said in Nagasaki Peace Park.
Attendees, including U.S. Ambassador Caroline Kennedy and representatives from dozens of other countries, observed a minute of silence at 11:02 a.m. local time, the moment that the plutonium bomb fell from the bomb bay of a U.S. B-29 and detonated over the city on Aug. 9, 1945.
The "three non-nuclear principles" to which Abe referred are Japan's policy of neither possessing nor producing atomic weapons and not allowing others to bring them into the country.
But as NPR's Anthony Kuhn reports from the city, Abe's remarks come at a time when Japan's government is pushing legislation to lift post-war restrictions on its ability to wage war.
"Japan's defence minister triggered a new row over controversial security legislation on Wednesday when he said the bills under consideration by parliament would not rule out the military transporting the nuclear weapons of foreign forces.
"Abe's cabinet adopted a resolution last year reinterpreting the pacifist constitution, drafted by Americans after World War Two, to let Japan exercise collective self-defence, or defend an ally under attack.
"The unpopular bills have already passed the lower house and Abe's ruling bloc has a majority in the upper house as well. But surveys show a majority of voters are opposed to what would be a significant shift in Japan's defence policy."
Anthony reports that 86-year-old Sumiteru Taniguchi, a young postman who was severely burned in the bombing, told the gathering that the security bill now before Japan's parliament will lead the country to war and is unacceptable.
"We cannot accept this," Taniguchi said.
Nagasaki Mayor Tomihisa Taue, speaking at the ceremony, urged Japan's leaders "to listen to these voice of unease and concern."
And United Nation's Secretary General Ban Ki-moon echoed calls to abolish nuclear weapons: "I wholeheartedly join you in sounding a global rallying cry: No more Nagasakis. No more Hiroshimas."