Support for Swedish and Finnish membership is strong among Democrats and Republicans in both chambers.

- It is seen as a great triumph for NATO's and the USA's fight against Russia that even the so far neutral Sweden is prepared to join the defense alliance, something that felt unthinkable just a year ago, says Andreas Utterström, communications consultant and USA connoisseurs.

Few intend to vote no

A few Republican members have announced that they intend to vote no.

- They have said that they will vote no because they think that the biggest threat to the United States is not Russia but China.

Then they think that you put the resources there instead of expanding NATO in a way that Russia perceives as a provocation, says Andreas Utterström.

But it is unlikely that these members' votes will affect the outcome of the vote, says Andreas Utterström.

- I don't see anything that can put a stop to this.

Those who vote no do so as a way to play for domestic opinion and not least Donald Trump, with whom they want to look good for the future.

Voting in the American debate begins with a debate that starts at 19:30 Swedish time.

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"A historic day" says Foreign Minister Ann Linde (S) about the ambassadors of all NATO countries now signing Sweden's accession protocol to NATO.