AMNA NAWAZ: Let's turn now to our Nick Schifrin, who's in Munich for the annual security conference.

Nick, so how did this news about Alexei Navalny land in Munich?

NICK SCHIFRIN: Amna, it was a real shockwave.

That is the best way to describe this.

I was with the congress men and women and their staffs as this news came in.

And it was really received with horror that quickly became grief mixed with a lot of doubt about whether this was actually true.

Many of them have worked with Navalny and his staff for many years.

And many of them quickly started putting together statements that would blame Putin, that would blame the Kremlin, even though there's no official confirmation.

It also instantly changed the conversation.

As you know, Amna, a lot of the conversation coming into this conference was about former President Donald Trump and his comments about NATO.

It was about the U.S. failure to be able to deliver from Congress absolutely vital military aid to Ukraine that it needs in the next few weeks.

And, instantly, the conversation became instead about Russia and Putin.

AMNA NAWAZ: So, Nick, as you say, much of that conversation focused on former President Trump and on Ukraine before the news out of Russia.

But what about the conversation about former President Trump and NATO and Ukraine?

Where was that today?

NICK SCHIFRIN: Yes, still very, very much going through the halls of this international security conference.

And perhaps it's no surprise that, at an international security conference, most of the audience believes in international security cooperation.

So perhaps Vice President Kamala Harris earlier today was playing to the crowd when she suggested former President Donald Trump, whose name she did not actually use, was the outlier for suggesting that the U.S. should not defend countries that do not meet that 2 percent GDP threshold of defense spending.

KAMALA HARRIS, Vice President of the United States: However, there are some in the United States who disagree.

They suggest it is in the best interest of the American people to isolate ourselves from the world.

Let me be clear.

That world view is dangerous, destabilizing, and indeed shortsighted.

NICK SCHIFRIN: One of the attendees here is Estonian Prime Minister Kaja Kallas.

I asked her earlier tonight to first respond to the news about Alexei Navalny.

KAJA KALLAS, Prime Minister of Estonia: Putin's playbook hasn't changed.

I mean, we have seen a long list of political competitors that he has eliminated.

So this is not a surprise, considering that he has been torturing Navalny for years already.

This is the way dictators work.

In dictator's handbook, what do you do?

You eliminate all the alternatives, so that the cronies around you, when they see that you are going to the wrong direction, they have nowhere to turn to because there is no alternative.

NICK SCHIFRIN: Was Navalny murdered?

KAJA KALLAS: Well, I can't say that because we don't know.

We don't see.

But it's clearly that the intention of the poisoning that took place some time ago, the imprisonment and the way he was treated there, he was not treated well.

NICK SCHIFRIN: This week, the Estonian foreign intelligence service released a new assessment that says Russia is preparing for military confrontation with the West within the next decade.

What is that based on, and can it be prevented?

KAJA KALLAS: It can be prevented if we invest in our defense, because, if you think about the aggressor, the aggressor takes the step of attacking somebody when he thinks that he can win, because the other side is weaker.

So we haven't taken the defense seriously enough.

And that means all the NATO allies have to do more.

NICK SCHIFRIN: We have been focusing on Europe, but I want to ask about the U.S. Is the United States a reliable partner?

KAJA KALLAS: Of course, all these statements from the United States are making us worried, because the United States has been the biggest ally.

And, I mean, the only time Article 5 has been used is when the U.S. called us.

This is something that we need to do together.

I mean, when you have aggression that pays off some part in the world, it will invite other aggressors in the world to start wars elsewhere.

NICK SCHIFRIN: Does Europe need to assume that the United States cannot defend Europe and cannot provide perhaps Europe a nuclear umbrella anymore?

KAJA KALLAS: I don't think so.

We have the agreements in place in NATO, all the structures in place.

What we definitely have to do ourselves is to do more, like I said before.

But, I mean, the United States has been a reliable partner.

And, of course, we hope that it's going to be in the future as well.

NICK SCHIFRIN: You say "We hope."

Former President Trump, of course, has said twice now in the last week or so that perhaps the U.S. should not defend NATO allies that do not meet that 2 percent GDP threshold.

Perhaps the U.S. Congress can restrain a future President Trump from leaving NATO, but isn't the damage already done?

I mean, isn't the damage to Article 5 the doubt that is being sown here that the U.S. wouldn't come to NATO's allies?

KAJA KALLAS: It has been a wake-up call for many European countries that haven't done enough.

And I think that is a positive thing if they start to do more.

But, of course, statements like this, we are watching them and trying to figure out, but this is not the surprise.

I mean, President -- presidential candidate Trump, when he was president, he had the same ideas.

But what I want to say is that over 60 percent of American exports go to Europe, not to Asia, but to Europe.

So, it is actually to the benefit of your people, your jobs, your employment, your, I mean, prosperity that we are so, I mean, really tied to each other.

So, if something happens in Europe, that has a very clear effect on American economy.

NICK SCHIFRIN: The U.S. House of Representatives so far has not accepted sending more military aid to Ukraine.

In Eastern Ukraine, we're already seeing Avdiivka about to fall to Russia because of a shortage that already exists for Ukrainian weapons.

And there's also worries that, without this military aid, Ukraine will run short of air defense just in the next few months.

Some I talked to are worried that Ukraine will lose the war if the U.S. House does not send that money.

Do you share that concern?

KAJA KALLAS: Definitely, we have to help Ukraine.

And we have to help them more, I mean, because they are defending their country.

If you think about the countries in the Ramstein coalition that are supporting Ukraine militarily, so the combined defense budgets of the Ramstein coalition are 13 times bigger than that of Russia's heavily inflated one.

So... NICK SCHIFRIN: But without the U.S., doesn't that number change dramatically?

KAJA KALLAS: But, actually -- actually, Europe has done more than U.S.

But, of course, America has a very, very important share there.

So it is something that we have actually calculated.

If all the Ramstein coalition countries would commit to 0.25 percent of the GDP in military aid to Ukraine, this breaking point for the war could be there.

NICK SCHIFRIN: But, finally, Ukraine has been sent more than $80 billion of military aid from the West.

This past year, it did not achieve even its lowest goals for the counteroffensive.

What can it achieve with more military aid, even if the House releases it, that it hasn't already?

KAJA KALLAS: Well, if they have long-distance weapons, if they have real weapons to defend themselves, then they can push back Russia as well.

So, the breaking point in all these elements could be actually much nearer.

But, of course, we can't also say that let's just walk away and say that, OK, you get this territory and the aggression pays off.

If the aggression pays off, it serves as an invitation to use it elsewhere.

And then we will wake up in a much more dangerous world.

NICK SCHIFRIN: So, how do you see this war ending?

KAJA KALLAS: I see this war ending with Russia going back to Russia.

That is actually very, very simple and easy.

NICK SCHIFRIN: Prime Minister Kaja Kallas, thank you very much.

KAJA KALLAS: Thank you.