Sweden and Finland have the "full, total and complete backing" of the US in their decision to apply for Nato membership, President Joe Biden said.
Speaking alongside Swedish Prime Minister Magdalena Andersson and Finnish Prime Minister Sauli Niinisto at the White House on Thursday, Biden called Sweden and Finland's applications "a watershed moment in European security", reports the BBC.
"New members joining Nato is not a threat to any nation," Biden said, adding that having two new members in the "high north" would "enhance the security of our allies and deepen our security co-operation across the board".
Sweden and Finland submitted their applications to be part of the Western defence alliance this week, marking a major shift in European geopolitics.
To join the alliance, the two nations need the support of all 30 Nato member states. But the move by the Nordic nations has been opposed by Turkey.
Russia has repeatedly said it sees Nato as a threat and has warned of "consequences" if the block proceeds with its expansion plans.