PRESIDENT OBAMA: Good morning, everybody. It is my privilege to welcome you to Washington and to formally convene our fourth Nuclear Security Summit. I convened our first summit – six years ago, in this same room – because the danger of a terrorist group obtaining and using a nuclear weapon is one of the greatest threats to global security.

　　Our nations committed ourselves to action – concrete, tangible steps to secure the world’s vulnerable nuclear materials. And we continued our work at our summits in Seoul and The Hague. I want to, again, thank our friends from the Republic of Korea and the Netherlands for their leadership on this critical issue.

　　Back at our first summit, I quoted Albert Einstein. At the dawn on the nuclear age, he said, “The unleashed power of the atom has changed everything.” And he added, “A new type of thinking is essential if mankind is to survive.” Over the past six years, when it comes to nuclear security, 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. It requires coalitions and sustained coordination across borders and institutions. And the good news is we’ve made significant progress.

　　We’ve made nuclear security a priority at the highest levels. And I want to thank all my fellow leaders – from more than 50 nations and key international organizations – for your commitment to this work and being here today. Some of you were here for our very first summit; many of you have since taken office and joined this work. But it’s a reminder that the task of protecting our citizens transcends political ideologies, parties and administrations.

　　To date, our nations have made some 260 specific commitments to improve nuclear security – and so far, three-quarters of these steps have been implemented. More than a dozen nations have removed all their highly enriched uranium and plutonium. Countries have removed or disposed of several tons of this deadly material. Nations have improved their nuclear security, including stronger regulations and more physical security of nuclear facilities, and more nations are cooperating to prevent nuclear smuggling.

　　Leading up to this summit, nations have fulfilled additional commitments. Argentina, Switzerland, Uzbekistan all successfully eliminated all their highly enriched uranium from their countries. China recently opened its new center for promoting nuclear security and training, and I’m pleased that the United States and China are cooperating on nuclear security. And Japan is working to complete the removal of more than half a ton of highly enriched uranium and plutonium, which is the largest project in history to remove nuclear material from a country.

　　I’m also pleased to announce that in recent days, after many years of work, 102 nations have now ratified a key treaty – the Convention on the Physical Protection of Nuclear Material. As a result, we expect that the treaty will enter into force in the coming weeks – giving us more tools that we need to work together in the event of theft of nuclear material or an attack on a nuclear facility. Several of the nations here made the extra effort in recent weeks to complete this process in time for this summit. And I want to thank you very much for helping us get over the line.

　　Once again, I’m making it clear that the United States will continue to do our part. Today we’re releasing a detailed description of the security measures our military takes to protect nuclear material so that other nations can improve their security and transparency as well.

　　For the first time in a decade, we’re providing a public inventory of our stockpiles of highly enriched uranium, which could be used for nuclear weapons, and that inventory is one that we have reduced considerably. When it comes to our nuclear-powered ships and submarines, we’re exploring ways to further reduce our holdings of highly enriched uranium.

　　In short, everybody has been participating, and by working together, our nations have made it harder for terrorists to get their hands on nuclear material. We have measurably reduced the risk. But as we discussed at last night’s dinner, the threat of nuclear terrorism persists and continues to evolve. Fortunately, because of our coordinated efforts, no terrorist group has succeeded thus far in obtaining a nuclear weapon or a dirty bomb made of radioactive materials. But we know that al Qaida has long sought nuclear materials. Individuals involved in the attacks in Paris and Brussels videotaped a senior manager who works at a Belgian nuclear facility. ISIL has already used chemical weapons, including mustard gas, in Syria and Iraq. There is no doubt that if these madmen ever got their hands on a nuclear bomb or nuclear material they most certainly would use it to kill as many innocent people as possible.

　　And that’s why our work here remains so critical. The single most effective defense against nuclear terrorism is fully securing this material so it doesn’t fall into the wrong hands in the first place.

　　This is difficult. At hundreds of military and civilian facilities around the world, there’s still roughly 2,000 tons of nuclear material, and not all of this is properly secured. And just the smallest amount of plutonium – about the size of an apple – could kill and injure hundreds of thousands of innocent people. It would be a humanitarian, political, economic, and environmental catastrophe with global ramifications for decades. It would change our world.

　　So we cannot be complacent. We have to build on our progress. We have to commit to better security at nuclear facilities; to removing or disposing of more dangerous material; to bringing more nations into treaties and partnerships that prevent proliferation and smuggling; and to making sure that we have the architecture in place to sustain our momentum in the years ahead.

　　With so many members of the global coalition against ISIL here today, this will also be an opportunity to make sure that we’re doing everything in our power to keep a terrorist group like ISIL from ever getting its hands not just on a nuclear weapon, but any weapon of mass destruction.

　　So I am very appreciative of the excellent work that’s been done and the excellent conversation we had last night. With that, what I’d like to do is to invite Prime Minister Mark Rutte of the Netherlands to review some of the specific progress that we’ve made since our last summit.

（编辑：何莹莹）