JIM LEHRER: The Obama administration today called on China to help solve a number of the world's problems, including reining in North Korea.
Ray Suarez has that story.
U.S. SECRETARY OF STATE HILLARY RODHAM CLINTON: America and China have arrived at a critical juncture.
RAY SUAREZ: In a major policy address at the State Department today, Secretary of State Hillary Clinton said a summit next week between President Obama and Chinese President Hu Jintao must produce real action on real issues: trade, climate change, recession and North Korean nuclear proliferation.
She also urged China to assume the responsibilities of being a world power in the 21st century.
HILLARY RODHAM CLINTON: But that means accepting a share of the burden of solving common problems, abiding by and helping to shape a rules-based international order.
RAY SUAREZ: Clinton emphasized one of those burdens was North Korea. She challenged China to get more involved in reining in Pyongyang.
HILLARY RODHAM CLINTON: We fear -- and have discussed this in depth with our Chinese friends -- that failure to respond clearly to the sinking of a South Korean military vessel might embolden North Korea to continue on a dangerous course.
RAY SUAREZ: Defense Secretary Robert Gates was in China earlier this week aiming to improve U.S.-China military relations. He then went on to Japan and South Korea.
Today, in Tokyo, Gates reinforced that idea that relations between the countries need to be bolstered.
U.S. SECRETARY OF DEFENSE ROBERT GATES: It is North Korea's pursuit of nuclear weapons and the proliferation of nuclear know-how and ballistic missile equipment that have focused our attention, developments that threaten not only the peninsula, but the Pacific Rim, and international stability as well.
RAY SUAREZ: Margaret Warner has been reporting in South Korea since the new year.
I spoke with her earlier today about the situation on the Korean Peninsula.
Margaret, Secretary of Defense Gates visited Seoul on his way home from China and Japan. What was on the agenda?
MARGARET WARNER: Ray, this was really a message of solidarity to China, to North Korea, and to the world that the U.S. and South Korea stand together in how to deal with the North Korean threat, both their attacks on the South recently and their missile and nuclear programs.
Secretary Gates did say today that he thought dialogue could resume between North and South, talks could resume among the six nations talking about the nuclear program. But he stood by the South in its insistence that, before they'll sit down with the North, the North has to be ready to talk about what they did last year.
So, the basic message was, U.S. is eager to get talks going, but no one is going to split Washington and Seoul.
RAY SUAREZ: Of course, you are referring to that attack by the North Koreans on a South Korean-held island around Thanksgiving.
Is South Korea on edge? Is the country still living in the shadow of that very provocative North Korean assault?
MARGARET WARNER: Ray, I would say that people's anxiety level has calmed a little bit, compared to what it was described to be like last November and December. But there's a new mood here, a new soberness about the threat from the North.
Fifty South Koreans total were killed last year in two attacks by the North, the other one on a warship. And the ones killed in November were the first civilians sort of deliberately targeted. And, so, if you talk to South Korean people, as we have in the streets and in shops here, they have a new appreciation for the seriousness of the threat from the North.
And, as you know, the DMZ and the border with the North is just 30 miles up the road from the downtown behind me.
RAY SUAREZ: In the past, it appears that North Korean unpredictability has really kind of worked for the country, while South Korea has tried to build down tensions between the two countries.
But it sounds like, this time around, there is more of a resolve, more of a willingness to get tough with the North. You interviewed the South Korean national-security adviser. What did he have to say?
MARGARET WARNER: Ray, you're absolutely right. The national-security adviser, just after the Gates meetings, I met with him at some length.
And he was very firm about the fact that they wouldn't sit down with the North until, as I said, the North was ready to talk about what the North did last year, some of which they have been denying. What was interesting to me was the rationale, that, despite the threat the North poses militarily, this government in the South thinks they have got the North in a bit of a box.
Chun said that he thought North Korea's economy was in such dire shape, that they face what he called an existential crisis and that, unless the North agrees to denuclearize in exchange for aid, financial, food and fuel, that they could be closer to collapse than most people think. Now, he didn't use the word collapse, but that was the clear implication of what he said.
We have an excerpt.
CHUN YUNG-WOO, South Korean national-security adviser: Well, nobody can tell with confidence how long they will survive.
I don't think they can go on like that forever, without fixing their economy, without reviving their economy. And I don't think they can turn their economy around without massive outside assistance. I think the energy for change in North Korea is growing. We do not know when this energy will reach critical mass.
RAY SUAREZ: You have mentioned that Seoul is very close to the North Korean border. Do you get the sense when you are there that this is a city always on defensive alert that always has to be thinking about the possibility of an attack?
MARGARET WARNER: Absolutely, Ray, because it's so close, and because of the way the North has amassed its forces.
Remember that the North has the fourth-largest army in the world, over a million men, huge, huge network of artillery systems, 13,000 or so, the largest special-ops forces, I'm told, in the world. And most of it, 70 percent of it, in the last couple of decades has been moved right up against the DMZ.
Now, a lot of it is hidden underground, but right up against the DMZ, as I said, so close to where we are standing here. So, the prospect of surprise attack is a very real one. And that's not to mention the fact that, of course, they've got missiles. They have got enough plutonium for, it's believed, six nuclear devices, and, authorities here believe, potentially thousands of North Korean sleeper agents embedded in South Korean society.
RAY SUAREZ: Next week, you will have a series of reports on the NewsHour. Tell us what you are covering.
MARGARET WARNER: Well, Ray, we're going to take a closer look at this military standoff, the North-South tensions, what's behind it, where it's going.
We're really going to spend an entire piece just talking to ordinary South Koreans about how they feel and how their feelings have evolved. And then, for something different, we're going to look at the South Korean education system, which with, you may know, produces students that score in the highest ranks internationally, frankly, far ahead of the United States. And, of course, we will be keeping a close eye on South Korea's reaction to the Hu visit to Washington.
RAY SUAREZ: Margaret, good to talk to you. Stay warm.
MARGARET WARNER: Thanks, Ray.