After a debate lasting over three hours, the American senators voted yes to ratify Sweden's and Finland's applications to join the NATO defense alliance.

The message came shortly after midnight during the night towards Thursday, Swedish time.

Ann Linde describes it as a "great success" that the US Congress has voted yes.

- It is the largest and most important country in NATO, so of course it plays a big role.

Now there are only seven countries left that have not ratified, it has never gone so quickly, she says.

The countries' two US ambassadors, Karin Olofsdotter and Mikko Hautala, were invited to follow the process directly in the Senate.

A few Republican senators had announced in advance that they intended to vote no, but otherwise support has always been strong among Democrats and Republicans in both chambers.

"Success for national security"

Senate Republican leader Mitch McConnell has been clear in his support, visiting both countries in May.

Ahead of Wednesday's vote, he stressed the importance of voting yes.

- Their entry will make NATO stronger and America safer, he said when he spoke in the Senate.

- This is a national security hit that deserves unanimous support from both parties.

Several of the politicians highlighted both countries as robust democracies with strong economies and modern defense forces.

Democrat Amy Klobuchar called a yes vote a "warning shot to tyrants around the world," while Republican Tom Cotton said Sweden and Finland will be "two of the alliance's strongest members the second they join."

23 countries have said yes

Dag Blanck, professor of North American studies at Uppsala University, explains that Swedish and Finnish membership is above all seen as a strengthening of the defense alliance.

The US thus sees it as strategically, militarily and geographically advantageous.

Can the decision affect the countries that have not voted yet?

- It is difficult to say anything about it, but the USA is the leading country in NATO, so it sends an important signal that you want to have Sweden and Finland with you.

According to Dag Blanck, the biggest question mark is how Turkey will vote.

The US has therefore made it very clear to Turkey that this is an important issue for them.

With the USA, 23 out of 30 NATO countries have approved Sweden's and Finland's application.