GEOFF BENNETT: President Trump has promised to remake American foreign policy and today vowed that the U.S. State Department will have, in his words, an America first foreign policy.

Nick Schifrin looks at how the world is watching the inauguration of the 47th president.

NICK SCHIFRIN: Much of the world has responded with congratulations today, from the Chinese Foreign Ministry, to Canadian Prime Minister Justin Trudeau, to Israeli Prime Minister Benjamin Netanyahu, who vowed victory over Iran with Trump's help.

But after Trump said in his inaugural address that Panama had -- quote -- "violated the spirit" of the treaty that governs the canal, Panamanian President Jose Mulino said: "Dialogue is always the way to clarify the points mentioned without undermining our right, total sovereignty and ownership of our canal."

In Europe there were also regards the new president, but leaders also took the opportunity to pledge change and debate the future of the war in Ukraine.

And to discuss that, we turn to Jens Stoltenberg, the most recent secretary-general of NATO, who will become the chairman of the Munich Security Conference next month.

Jens Stoltenberg, thanks very much.

Welcome back to the "News Hour."

Let's start in Ukraine.

Today, President Zelenskyy made a statement that said -- quote -- "Trump's peace through strength provides an opportunity to strengthen American leadership and achieve a long-term and just peace."

Russian President Vladimir Putin said he welcomed Trump's statement to restore direct contact and prevent World War III.

Do you believe this is the right time to talk peace in Ukraine?

And do you believe that the Trump administration will help Ukraine achieve a just peace?

JENS STOLTENBERG, Former NATO Secretary-General: Well, I think it's a bit too early to tell.

But what is obvious is that we all want this war to end.

At the same time, we know that the quickest way of ending the war is to lose the war.

But that will not bring peace.

That will bring occupation.

So, the challenge is to ensure that Ukraine is able to end the war in a way that Ukraine prevails as a sovereign independent nation.

And the only way to do that is to convince President Putin that he will not win on the battlefield.

And that means that we need to provide military support to Ukraine and also to arm and strengthen the Ukrainians, so they can deter future aggression.

NICK SCHIFRIN: Down at Mar-a-Lago, before he became president, President Trump said that he understood why Russia did not want Ukraine -- quote -- "on its doorstep" and then NATO, suggesting he would reverse decades of U.S. open-door policy of European countries to join NATO.

Was that a mistake?

JENS STOLTENBERG: I'm from Norway.

And Norway is a small country bordering Russia.

We were the only European country bordering the Soviet Union when NATO was established in '49.

Russia and Moscow didn't like that.

They said it was a provocation, a threat.

But I'm glad that the other allies said, well, if Norway wants to join, Norway's welcome, in the same way are welcome, for instance, that now Sweden and Finland has decided and are now full members of the alliance.

It is the right of every free, independent nation to choose its own path.

And that includes what kind of security arrangements it wants to be part of.

And, therefore, NATO's door should remain -- or should, yes, remain open, and we should continue to pursue the open-door policy.

NICK SCHIFRIN: I have talked to multiple senior European leaders over the last few months.

And they all say that they want to work with the Trump administration ON Ukraine, on NATO, even on places like Lebanon, where the Trump administration will need European help.

But they warn that, if the Trump administration imposes tariffs on Europe, that cooperation would be more difficult.

Do you agree?

JENS STOLTENBERG: Yes, I think that's a factual thing.

I understand that the United States and also other allies are concerned about trade, overdependence on raw materials, products from authoritarian countries, like we have seen, for instance, overdependence on Russian gas or rare earth minerals from China.

But it's a total different thing to be concerned about free trade among free nations.

And I strongly believe that, among friends and allies, and especially among NATO allies, we are 50 percent of the world global economy, that we should have free trade.

That will increase growth.

It will make us all richer.

And, therefore, I think we should not impose tariffs against allies, but keep our economies open to each other.

NICK SCHIFRIN: Brussels does plan economic countermeasures if the Trump administration chooses tariffs.

Would that trade war imperil transatlantic cooperation?

JENS STOLTENBERG: It will weaken the transatlantic bond, because the transatlantic bond is about security, defense.

And European allies are stepping up, investing more.

But the transatlantic bond is also about trade.

And, again, I believe that we are getting richer, more wealthy, all of us, when we trade.

NICK SCHIFRIN: Finally, Jens Stoltenberg, we went back to the archive and found this moment from a breakfast you held with the former president in 2018.

DONALD TRUMP, President of the United States: But Germany, as far as I'm concerned, is captive to Russia because it's getting so much of its energy from Russia.

So we're supposed to protect Germany, but they're getting their energy from Russia.

Explain that.

And it can't be explained.

You know that.

NICK SCHIFRIN: You have worked with Trump for years.

What do you recommend to fellow European leaders who are about to work with him as president for the next four years?

JENS STOLTENBERG: I recommend to do the same as we did last time President Trump was president.

I'm not saying that everything will be easy, but I'm saying that friends and allies should sit down, discuss, engage, and then find common ground also on the issues where there are disagreements.

NICK SCHIFRIN: Jens Stoltenberg, thank you very much.

JENS STOLTENBERG: Thanks so much for having me.