Finnish President Sauli Niinistö released a video on Saturday afternoon, which revealed part of the conversation between the Finnish president, US President Joe Biden and Swedish PM Magdalena Andersson Tuesday last week.

US President Biden signed the Nordic countries' Nato accession documents in Washington on Tuesday evening Finnish time, after a week earlier the US Senate ratified their accession in a vote of 95 to one.

In the video Biden assures his strong support for Finland and Sweden.

"You have 110 percent of my support. Just pick up the phone and I'll be at your service," Biden said in the video.

According to the US president, Finland and Sweden are already increasing the security of their region, and Nato membership only makes it official.

In the video, all three emphasise the strength of the countries' mutual partnership.

"Communication is close and continuous between the United States and Finland and also Sweden. Partners bring security. In the video, snippets of the atmosphere from Tuesday's call with President Biden and Prime Minister Andersson," Niinistö wrote in a tweet sharing the video.

Official Twitter accounts of the US President and the Prime Minister of Sweden have also shared the video.

The Finnish Office of the President said that the video was made in cooperation with the White House.