AMNA NAWAZ: Ahead of Europe's largest annual security conference, NATO defense ministers gathered in Brussels today to calm nerves and stiffen spines after President Trump's threats to Greenland roiled the alliance.

Here's Nick Schifrin with more.

NICK SCHIFRIN: Today, an alliance recently shaken by American threats hosted a reunion to portray itself a happy family.

NATO defense ministers met in Brussels and provided words of encouragement and reassurance, including to themselves.

BORIS PISTORIUS, German Defense Minister: USA are a member of NATO, and they will remain a member of NATO.

But to keep -- in order to the keep the NATO -- to NATO transatlantic, it is necessary to make it more European.

MARK RUTTE, NATO Secretary-General: Good to see you.

NICK SCHIFRIN: Europization of NATO, exactly the message from the Pentagon's number three, Elbridge Colby.

ELBRIDGE COLBY, U.S.

Undersecretary of Defense for Policy: And I think we have a really strong basis for working together in partnership, but putting NATO, kind of a 3.0 NATO that's based on a partnership, rather than dependency.

NICK SCHIFRIN: Today, the U.S.

says it provides nearly half of NATO's military posture and wants to provide less than one-third within about five years, especially as it prioritizes its own borders, Venezuela and the rest of Latin America, and China, whose military buildup is the fastest in world history.

As Colby told the defense ministers in a closed-door briefing: "We will continue to provide the U.S.

extended nuclear deterrent.

But Europe should feel the preponderance of the forces required to deter and if necessary defeat conventional aggression in Europe."

It's a message the Trump administration has sent consistently, but today's delivery was with a perhaps more constructive tone than one year ago today.

PETE HEGSETH, U.S.

Defense Secretary: We're also here today to directly and unambiguously express that stark strategic realities prevent the United States of America from being primarily focused on the security of Europe.

NICK SCHIFRIN: And last month.

DONALD TRUMP, President of the United States: The United States is treated very unfairly by NATO.

I mean, we have helped them for so many years.

We have never gotten anything.

And all we're asking for is to get Greenland, including right, title and ownership, because you need the ownership to defend it.

You can't defend it on a lease.

NICK SCHIFRIN: President Trump's implicit military threat against Greenland has passed.

But it sparked a new NATO plan called Arctic Century to boost surveillance and presence near Greenland and across the Arctic.

MARK RUTTE: We will also build a more cohesive picture of potential challenges in the Arctic, so that any gaps can be quickly and effectively addressed.

NICK SCHIFRIN: But across Europe and ahead of a key security conference in Germany, the Greenland hangover is lasting and sparking a fundamental question.

Is the U.S.

a reliable ally?