Russia has made a “massive strategic blunder” as Finland and Sweden look poised to join Nato as early as the summer, according to officials.

Washington is banking on the move that will stretch Russia’s military and enlarge the western alliance from 30 to 32 members as a direct consequence of President Putin’s invasion of Ukraine.

US officials said Nato membership for both Nordic countries was “a topic of conversation and multiple sessions” during talks between the alliance’s foreign ministers last week attended by Sweden and Finland. “How can this be anything but a massive strategic blunder for Putin?,” one senior American official said.

Finland’s application is expected in June, with Sweden expected to follow.