Nagasaki’s mayor criticized Japan’s government for a lack of effort on international nuclear disarmament as the country marked the 68th anniversary on Friday of the atomic bombing on the city.

Mayor Tomihisa Taue said Tokyo’s refusal in April to sign a statement rejecting unconditional use of nuclear weapons “betrayed expectations of the global community.”

Mr. Taue said the statement was signed by 80 countries and that Japan, the world’s only victim of atomic bomb attacks, contradicted its non-nuclear pledge by refusing.

“I call on the government of Japan to return to the origin of our pledge as an atomic-bombed country,” he said at a peace park near the epicenter of the blast.

The two atomic bombs the U.S. dropped on Hiroshima and Nagasaki in August 1945 prompted Japan’s surrender in World War II. The Hiroshima blast killed 140,000 people, and another 70,000 died in Nagasaki.

U.S. Ambassador John Roos attended Nagasaki’s event, a year after going to the anniversary ceremony at Hiroshima.

About 6,000 people attended Friday’s ceremony after offering silent prayers for the victims.

Mr. Taue also expressed concerns about Japan’s resumption of negotiations with India toward a nuclear cooperation agreement.

Despite the public’s safety concerns about nuclear energy since the Fukushima crisis, Prime Minister Shinzo Abe has been aggressively pushing to export nuclear plants and technology to emerging countries, including Turkey and Vietnam, and trying to step up cooperation with France and India.

Mr. Taue said nuclear cooperation with India, which has not signed the Nuclear Non-Proliferation Treaty would render the NPT framework toothless.

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