U.S. President Barack Obama hailed the “significant progress” the world’s nations have made on nuclear security, and pledged the United States will continue to cooperate with all efforts to reduce nuclear stockpiles and keep them safe.

Addressing more than 50 world leaders gathered at the Nuclear Security Summit in Washington, Obama said more than a dozen nations have disposed of their entire supplies of highly enriched uranium and plutonium — the radioactive elements necessary to build nuclear bombs.

During six years of international meetings on nuclear security — including four summits, which he initiated — the U.S. president said, “We’ve embraced a new type of thinking and a new type of action.”

“This is a perfect example of a 21st-century security challenge that no one nation can solve alone,” Obama told the leaders at a plenary session of the summit broadcast worldwide. “It requires coalitions and sustained coordination across borders and institutions. And the good news is we’ve made significant progress.”

Obama also met with a smaller gathering of the nations mostly closely involved in last year’s nuclear agreement with Iran. He told the so-called P5+1 group the deal with Iran “achieved a substantial success and focused on the dangers of nuclear proliferation in a real way.”

He stressed, however, that “full and continued implementation” of the Iran agreement will “take the same level of cooperation” from the international community.

Source-Voa