The next summit of NATO's heads of state and government will take place on December 3-4 in London to mark the alliance's 70th anniversary.

In announcing the dates, NATO Secretary-General Jens Stoltenberg said on May 23 that the meeting will be a chance to 'address current and emerging security challenges and how NATO continues to invest and adapt to ensure it will remain a pillar of stability in the years ahead.'

He added that London, which was home to NATO's first headquarters, was a fitting venue to mark 70 years of transatlantic military cooperation.

Britain and 11 other countries established the Western military alliance in 1949. There are now 29 member states and the headquarters is in Brussels.

The London summit comes amid persistent tensions between NATO and Russia and concerns about U.S. President Donald Trump's commitment to the alliance.

Trump has criticized NATO's European members of not spending enough on their armed forces.

NATO's founding act, the North Atlantic Treaty, was signed in April 4, 1949, in Washington by Belgium, Britain, Canada, Denmark, Iceland, France, Italy, Luxembourg, Netherlands, Norway, Portugal, and the United States. The alliance's 29 foreign ministers met for two days in Washington last month to mark the event.

Greece and Turkey joined together in 1952, followed by West Germany in 1955 and Spain in 1982.

After the fall of communism, Poland, the Czech Republic, and Hungary became members in 1999, followed by a second wave of expansion in the former Eastern Bloc in 2004, which brought Romania, Bulgaria, Estonia, Latvia, Lithuania, Slovakia, and Slovenia into the alliance.

Albania and Croatia were next, joining in 2009, and Montenegro became the newest NATO member in 2017.

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