Following a visit to a NATO summit in Vilnius, Air Force One landed at Helsinki Airport outside of the Nordic country's capital 10:00 pm local time (1900 GMT), an AFP photographer on board the aircraft reported.

The Nordic country, which shares a border with Russia of over 1,300 kilometres (800-mile), ended its historic military non-alignment to enter NATO as a response to the Russian invasion of Ukraine.

Biden will be the first US president to visit Helsinki since Donald Trump's summit five years ago with Russian President Vladimir Putin.

Besides Niinisto and the Finnish Prime Minister Petteri Orpo, Biden will meet on Thursday with other Nordic prime ministers, namely Sweden's Ulf Kristersson, Norway's Jonas Gahr Store, Denmark's Mette Frederiksen and Iceland's Katrin Jakobsdottir.

The topic of the discussions is cooperation between the Nordic countries and the United States on security, environmental and technology issues.

Finland will be Biden's final stop on his European tour before returning to Washington on Thursday after meeting Prime Minister Rishi Sunak in London on Monday and attending the Vilnius summit.

In Vilnius, Turkish President Recep Tayyip Erdogan suddenly reversed his stance on Sweden's NATO membership, after blocking the bid for more than a year and accusing Stockholm of harbouring Kurdish activists Ankara regards as terrorists.

The deal on Sweden followed a call with US President Joe Biden during which Erdogan raised both EU accession and Turkey's desire to acquire a large batch of F-16 fighter jets.

Biden's visit takes place following a contentious decision to provide Ukraine with cluster munitions, which most NATO member countries have banned but which the United States continues to hold.