“The US is the leading country in Nato, so it sends an important signal,” Dag Blanck, professor of North American Studies at Uppsala University, told TT news wire.

According to Reuters, the senate will vote on whether to approve or deny Sweden and Finland’s applications on Wednesday evening.

It seems unlikely that the US would vote against Sweden and Finland joining the alliance. There is broad support in both parties for accepting the countries’ bids to join Nato.

“The vast majority of Republicans and Democrats are in favour of Sweden joining Nato. It would be very surprising if they didn’t approve this,” Blanck said.

Only a few Republican senators have indicated that they will vote against the two countries joining.

“It’s not a lot of Republicans,” Blanck told TT. “There are some who on principle are against Nato expansion and the US’ engagement worldwide. So it’s nothing to do with Sweden, primarily,” he said.

Blanck believes that Sweden and Finland joining Nato is seen chiefly as a strengthening of the defence alliance. That is to say, it’s seen by many in the US as a positive development on a strategic, military and geographic level.

Sweden and Finland were invited to join the alliance on June 29th. All Nato members have now signed the two countries’ applications, but now each member’s parliament must also ratify accession protocols.

• EXPLAINED: The next five steps to a Swedish Nato membership

The speed at which this process can be carried out varies among member states, with 20 of 30 states having already approved Sweden and Finland’s application.

Once all Nato members have ratified accession protocols for each country, proof of ratification must be submitted to the US government, after which Sweden and Finland will become formal members of the Nato alliance.