Nato leaders are to meet outside of London for formal talks on Wednesday, as they gather to mark the military alliance's 70 th anniversary.
The talks will take place at a luxury hotel near Watford and follow receptions held on Tuesday at Buckingham Palace and Downing Street.
The two-day summit has so far been overshadowed by tension between allies.
Tuesday find sharp exchanges between US President Donald Trump and French President Emmanuel Macron.
The highly choreographed anniversary meet, intended to show unity, has been unable to hide deep differences between Nato members, BBC defence correspondent Jonathan Beale reports.
Although the 29 -member bloc's future is not in doubt, there are disagreements over Turkey's recent military action in northern Syria, relative levels of military spending by members and recent controversial remarks by President Macron that the alliance is “brain dead”.
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