AUDIE CORNISH, HOST:
President Obama is wrapping up an international summit aimed at better securing the world's nuclear weapons. He's been meeting in Washington this week with some 50 other world leaders. They're discussing steps they can take to prevent terrorists from getting their hands on nuclear material. NPR's Scott Horsley has been monitoring the summit, and he joins us now. And, Scott, this is the president's fourth and last nuclear security summit. Have the U.S. and other countries involved made any progress since the first one in 2010?
SCOTT HORSLEY, BYLINE: Audie, yes, some progress, though maybe not as much as some nuclear watch dogs would like. One result of this year's summit is that a treaty, which has been kicking around for about a decade, now finally has enough countries ratifying it to go into effect. And that treaty says countries have to take steps to ensure that civilian nuclear material is stored and protected and transported in a way that keeps it safe. That was one of several positive developments that the president touted today, and he also noted that since the first nuclear security summit back in 2010 about a dozen countries have gotten rid of their most dangerous nuclear stockpiles.
(SOUNDBITE OF ARCHIVED RECORDING)
BARACK OBAMA: By working together, our nations have made it harder for terrorists to get their hands on nuclear material. We have measurably reduced the risk.
HORSLEY: That said, though, Obama cautions there's still about 2,000 tons of nuclear material sitting at military and civilian sites around the world. Some of it not as well protected as it should be. And he says there's no doubt if terrorists got their hands on that material they could use it to kill a lot of innocent people.
CORNISH: And, of course, the terrorist group that a lot of people are talking about is ISIS, and that was clearly on the radar at this summit as well, right?
HORSLEY: Yeah, even as the administration says it's making headway against ISIS in its strongholds of Iraq and Syria, the president warns the terrorist group is still a potent threat.
(SOUNDBITE OF ARCHIVED RECORDING)
OBAMA: In fact, as ISIL is squeezed in Syria and Iraq, we can anticipate it lashing out elsewhere as we've seen most recently and tragically in countries from Turkey to Brussels.
HORSLEY: Now, in Brussels and last year in Paris, we saw that ISIS fighters are deadly enough with conventional weapons. But there was also evidence that the people behind the Brussels attack had monitored a Belgian nuclear official, raising the possibility ISIS might have set its sights on either nuclear sabotage or a dirty bomb. And for the participants at this nuclear security summit, that really highlighted the stakes.
CORNISH: Scott, one sidebar - President Obama also met privately with Chinese President Xi Jinping. How did that go?
HORSLEY: As usual, with the U.S. and China, Audie, it was kind of a mixed bag. The two leaders announced that they both plan to sign the Paris climate agreement at the first opportunity later this month. For these two countries, which are the biggest in the world, both in economic clout and in carbon emissions, that's another opportunity to show some leadership in battling climate change, and they're hoping other countries will follow suit. So that was the cooperative part where they pretty much see eye to eye. Obama and Xi are not so close, though, when it comes to China's conduct in international waters off its coasts and some of the territorial disputes between China and its neighbors. That's one of the issues, along with human rights and cybersecurity, where the U.S. and China have some serious differences. There is no indication that Obama and Xi bridged those differences during their meeting yesterday. But Obama did make some diplomatic references to what he called a candid exchange.
CORNISH: That's NPR's Scott Horsley. Scott, thank you.
HORSLEY: My pleasure, Audie. Transcript provided by NPR, Copyright NPR.