ARI SHAPIRO, HOST:

In the last day, President Trump has tweeted about Pakistan, Israel and the Palestinians, Iran and, perhaps most provocatively, North Korea. In that tweet, he said, quote, "North Korean leader Kim Jong Un just stated that the nuclear button is on his desk at all times. Will someone from his depleted and food-starved regime please inform him that I, too, have a nuclear button, but it is a much bigger and more powerful one than his, and my button works."

In response, Senator Bob Casey - a Democrat from Pennsylvania - tweeted (reading) this is exactly the kind of reckless behavior I was hoping we would avoid in 2018. Please, Mr. President, no more diplomacy via Twitter.

To talk about this distinctly Trumpian approach to foreign policy, Richard Haass joins us now. He's president of the Council on Foreign Relations and author of the book "A World In Disarray." Welcome.

RICHARD HAASS: Thank you.

SHAPIRO: Some of President Trump's defenders say his tweets are only words and that people should brush them off. Explain why you disagree with that.

HAASS: Tweets are White House statements. I worked at the White House under George Bush the father, and when the president would say something, it got scrubbed by the staff beforehand, often by the interagency - by the State Department, the Treasury, the Defense Department.

The words of the president are the most valuable currency the United States has in some ways. It's critical to reassuring allies. It's critical to informing the American public. It's critical to warning or deterring enemies out there.

So the idea that it would be done casually or impulsively seems to me to undermine one of the most important tools the president of the United States has in his possession.

SHAPIRO: If presidential words are currency and the currency is being spent in this way, what are the consequences of that?

HAASS: Well, it devalues the currency. So either the president means it, in which case some of this is truly counterproductive in terms of reassuring allies or trying to, say, avoid a conflict with a country like North Korea. Or he doesn't mean it, and these are, quote, unquote, "just tweets" or "just words." Well, that's never something you want to have happen where when the president speaks, other governments derive the lesson that they need not take it seriously.

So you can't have it both ways. Either people begin to forge different relationships, they substitute for the United States, or they take matters into their own hands.

SHAPIRO: So you're saying part of the fear here is that other world leaders - allies, adversaries and in between - will make partnerships that don't include the United States, make alliances that work around American leadership just because they can't count on the U.S. to be there?

HAASS: The short answer is, yes. I think we're beginning to see that. I think that you're seeing countries take matters into their own hands. The Saudis are becoming much more independent. I worry a little bit about a South Korea that's negotiating with North Korea.

I think it's important to see these tweets in a context. The United States has left the Paris climate agreement. We've pulled out of the Trans-Pacific Partnership. We've raised all sorts of question about our alliances. And I think other countries have basically said we can't assume anything about the United States anymore. We can't take anything for granted.

So what we've done is introduce a major element of uncertainty. And maybe I'm old-school here, but I want things to be calm. I like things to be predictable. I don't understand why the United States would want to wake up every morning and disrupt international relations when for the most part, we have been well-served by what has gone on in the world for the last 70 years.

SHAPIRO: Do you think it's possible that, done differently, foreign policy through Twitter could work and could be effective?

HAASS: I think there's a role for Twitter. I'd be hypocritical since I'm on it myself every day.

SHAPIRO: (Laughter).

HAASS: So I'm not against this or any president using Twitter. What I'm against is him using it in a way that's not as careful as any other statement or speech. Well, he has to remember that tweet is read not simply by, say, a political base within the United States but is read all around the world.

And you have to ask yourself before you press the send button, is this likely to advance American interests? Will this make it more or less difficult for us to get to where we want to get to? And I would think in many cases, these tweets are actually working against the very goals this administration has embraced.

SHAPIRO: Richard Haass is president of the Council on Foreign Relations, and his book, "A World in Disarray," is now out in paperback. Thanks so much for joining us.

HAASS: Thanks for having me. Transcript provided by NPR, Copyright NPR.

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