The Queen is to host a reception for Nato leaders at Buckingham Palace to mark 70 years of the alliance.
US President Donald Trump and French President Emmanuel Macron are among those expected to attend.
The evening event will take place on Tuesday December 3, the palace said, adding that further details will be announced in due course.
It is not yet known whether other members of the royal family will join the Queen for the celebration.
The next Nato leaders’ summit is taking place in Watford, Hertfordshire, in December, at The Grove hotel.
Mr Trump, who is set to meet heads of state, has repeatedly criticised the military alliance, describing it as “obsolete and disproportionately too expensive (and unfair) for the US”.
The controversial billionaire-turned-politician was feted with a ceremonial welcome and a banquet at Buckingham Palace during his state visit to the UK in June this year.
He later boasted about having “automatic chemistry” with the Queen, and praised her as a “spectacular woman”.
The American leader was met by tens of thousands of protesters in London before he attended a D-Day commemoration service in Portsmouth.
The cost of policing Mr Trump’s previous four-day visit to the UK in 2018, which included meeting the Queen at Windsor Castle and sparked swathes of demonstrations, came to £14.2 million.
The North Atlantic Treaty Organisation was established in Washington on April 4 1949.
It began as a 12-member alliance to counter-balance the growing military might of the Soviet Union and to keep the peace in post-war Europe.
The political and military alliance now has 29 member countries.