Updated at 11 a.m. ET
The reality of a possible nuclear attack from terrorists requires the world's nations to take on a new mindset for action, President Obama said today at the start of a plenary session of the Nuclear Security Summit.
Mr. Obama appealed to the dozens of world leaders before him to "summon the will, as nations, as partners, to do what this moment in history demands." With leaders from 47 countries convened, he said the threat of a nuclear confrontation between nations has gone down, but the risk of an attack from terrorists has gone up.
"It is increasingly clear that the danger of nuclear terrorism is one of the greatest threats to global security--to our collective security," the president said. "Today is an opportunity--not simply to talk, but to act. Not simply to make pledges, but to make real progress for the security of our people."
Already, the summit has resulted in some progress. China has agreed to work with the United States on possible sanctions against Iran for its nuclear build up, while the Ukraine has agreed to get rid of all of its highly enriched uranium.
Mr. Obama also announced this morning that President Lee Myung-bak of South Korea has agreed to host the next nuclear security summit in two years.
"We have the opportunity, as partners, to ensure that our progress is not a fleeting moment, but part of a serious and sustained effort," Mr. Obama said.
The president has already held two days of meetings with a few select world leaders. Today's meetings will include discussions about specific steps individual nations can take to secure loose nuclear materials, ways to strengthen the International Atomic Energy Agency, and international efforts to prevent terrorists from acquiring nuclear materials.
When the summit ends this evening, Mr. Obama hopes to have an international agreement for specific, concrete actions to secure loose nuclear materials within four years.
"I believe strongly that the problems of the 21st century cannot be solved by any one nation acting in isolation," Mr. Obama said. "They must be solved by all of us coming together."
The president touted steps the United States has taken to reduce its own nuclear arsenal and stop the spread of nuclear weapons: The Obama administration's revised nuclear policy narrows the circumstances under which the U.S. would use nuclear weapons.
Below is a group photo of the Heads of Delegation attending the Nuclear Security Summit in Washington.More on the nuclear summit: