AMNA NAWAZ: In the day's other news: The Trump administration today once again put Europe on notice, as European leaders met to try and coalesce around a new defense plan.

President Trump said he would selectively abide by Article 5, which commits the U.S. to defend NATO countries.

And a senior official blamed Ukraine itself for the U.S. pause on military and intelligence support ahead of a planned U.S.-Ukraine meeting next week.

Here's Nick Schifrin with more.

DONALD TRUMP, President of the United States: I view NATO as potentially good, but you have got to get some good thinking in NATO.

NICK SCHIFRIN: Today, in the White House, President Trump questioned one of the U.S.' most consequential commitments, to defend any NATO country that is attacked.

DONALD TRUMP: If they don't pay, I'm not going to defend them.

No, I'm not going to defend them.

NICK SCHIFRIN: President Trump has long complained that European countries don't spend enough on defense.

Today, 23 of 32 spend at least 2 percent of their GDP on defense, but President Trump doubts their commitment to common defense known as Article 5.

Europeans are trying to erase those doubts, and tonight endorsed a rearm plan, expanding the E.U.

's defense spending by $800 billion and giving governments money to invest in Ukrainian weapons or buy American weapons to send to Ukraine.

Polish President Andrzej Duda speaking at NATO: ANDRZEJ DUDA, Polish President (through translator): If the whole of NATO does not increase their defense spending, then, unfortunately, possibly, Vladimir Putin would be eager to attack again because there would not be enough of a deterrent.

NICK SCHIFRIN: On the red carpet in Brussels today, Europe and Ukraine standing shoulder to shoulder.

VOLODYMYR ZELENSKYY, Ukrainian President: You made a strong signal to Ukrainian people, to Ukrainian warriors, to civilians to all our families.

And it's great that we are not alone.

We feel it and we know it.

NICK SCHIFRIN: But Ukraine also feels nightly Russian attacks.

And once again today, Russia struck a civilian target, this time a hotel in President Zelenskyy's hometown in Southern Ukraine, where American volunteers were staying, including Adam.

ADAM, American Volunteer in Ukraine: I'm sure there's a reason that we have all survived, and it's so that we can continue to help Ukraine for as long as it takes.

Ukraine is a wonderful country and is an example to the world for democracy, freedom.

LT. GEN. KEITH KELLOGG (RET.

), Special Envoy to Ukraine and Russia: Very candidly, they brought it on themselves.

NICK SCHIFRIN: But 5,000 miles away, Special Envoy to Ukraine in Russia Keith Kellogg blamed Zelenskyy for the U.S. decision to pause intelligence and military aid.

LT. GEN. KEITH KELLOGG: You don't negotiate peace discussions in public.

You don't try to challenge the president of the United States in the Oval Office that, in fact, you need to side with me and not the Russians.

It is sort of like hitting a mule with a two-by-four across the nose.

You got their attention.

This is one of those, listen to me.

We're serious about this.

And you need to understand we're serious about this.

And this is one of the ways we made sure they understood.

NICK SCHIFRIN: And he suggested the meeting between Special Envoy Steve Witkoff and Russian President Vladimir Putin produced an understanding.

LT. GEN. KEITH KELLOGG: We are aware.

It's sort of like a quid pro quo, where you want to go and what you want to do and the discussions that were made.

And it's...

QUESTION: Is their term sheet, essentially?

LT. GEN. KEITH KELLOGG: Well, I use the term, term sheet.

And term sheet is -- the answer is, yes, in generalization.

NICK SCHIFRIN: Ukrainian soldiers and their commanders have described U.S. policy shifts as a betrayal, as voiced today by Ukraine's former army chief and current ambassador to London, Valerii Zaluzhnyi.

VALERII ZALUZHNYI, Ukrainian Ambassador to the United Kingdom (through translator): It is not only Russia and the axis that is trying to destroy the world order, but the United States of America is actually destroying it completely.

NICK SCHIFRIN: Senior Trump officials say that is not the president's intention, but they say he does intend to unsettle and disrupt.

And Ukraine feels that its survival is at stake.

For the "PBS News Hour," I'm Nick Schifrin.