LONDON, UNITED KINGDOM - DECEMBER 04: (front row ) Britain's Prime Minister Boris Johnson (5L), NATO Secretary General Jens Stoltenberg (6L), US President Donald Trump (5R) and President of Turkey Recep Tayyip Erdogan (4R), (middle row) France's President Emmanuel Macron, German Chancellor Angela Merkel, Greek Prime Minister Kyriakos Mitsotakis, Hungary's Prime Minister Viktor Orban, Iceland's Prime Minister Katrin Jakobsdottir, (top row) Netherland's Prime Minister Mark Rutte, Norway's Prime Minister Erna Solberg, Lithuania's Prime Minister Saulius Skvernelis, Portugal's Prime Minister Antonio Costaa and Montenegro's Prime Minister Dusko Markovic gather for the family photo at the NATO summit at the Grove Hotel in London on December 4, 2019. ( Mustafa Kamaci - Anadolu Agency )

LONDON, UNITED KINGDOM - DECEMBER 04: US President Donald Trump (C) is welcomed by British Prime Minister Boris Johnson (R) and NATO Secretary-General Jens Stoltenberg (L) during the NATO Summit in London, United Kingdom on December 4, 2019. ( Mustafa Kamacı - Anadolu Agency )

LONDON, UNITED KINGDOM - DECEMBER 04: US President Donald Trump (C) is welcomed by British Prime Minister Boris Johnson (R) and NATO Secretary-General Jens Stoltenberg (L) during the NATO Summit in London, United Kingdom on December 4, 2019. ( Mustafa Kamacı - Anadolu Agency )

LONDON, UNITED KINGDOM - DECEMBER 04: US President Donald Trump (C) is welcomed by British Prime Minister Boris Johnson (R) and NATO Secretary-General Jens Stoltenberg (L) during the NATO Summit in London, United Kingdom on December 4, 2019. ( Mustafa Kamacı - Anadolu Agency )

LONDON, UNITED KINGDOM - DECEMBER 4: (----EDITORIAL USE ONLY – MANDATORY CREDIT - "TURKISH PRESIDENCY / HANDOUT" - NO MARKETING NO ADVERTISING CAMPAIGNS - DISTRIBUTED AS A SERVICE TO CLIENTS----) President of Turkey Recep Tayyip Erdogan (R) meets U.S. President Donald Trump (L) during the NATO Leaders' Summit in London, United Kingdom on December 4, 2019. ( TURKISH PRESIDENCY / HANDOUT - Anadolu Agency )

LONDON, UNITED KINGDOM - DECEMBER 4: (----EDITORIAL USE ONLY – MANDATORY CREDIT - "TURKISH PRESIDENCY / HANDOUT" - NO MARKETING NO ADVERTISING CAMPAIGNS - DISTRIBUTED AS A SERVICE TO CLIENTS----) President of Turkey Recep Tayyip Erdogan (R) meets U.S. President Donald Trump (L) during the NATO Leaders' Summit in London United Kingdom on December 4, 2019. ( Turkish Presidency/Handout - Anadolu Agency )

LONDON, UNITED KINGDOM - DECEMBER 04: US President Donald Trump (front) is welcomed by NATO Secretary-General Jens Stoltenberg (L) during the NATO Summit in London, United Kingdom on December 4, 2019. ( Mustafa Kamacı - Anadolu Agency )

LONDON, UNITED KINGDOM - DECEMBER 4: Nato Secretary General Jens Stoltenberg (L) and German Chancellor Angela Merkel (R) shake hands during the NATO Leaders' Summit in London, United Kingdom on 04 December 2019. ( Mustafa Kamaci - Anadolu Agency )

LONDON, UNITED KINGDOM - DECEMBER 04: US President Donald Trump (R) is welcomed by British Prime Minister Boris Johnson (L) during the NATO Summit in London, United Kingdom on December 4, 2019. ( Mustafa Kamacı - Anadolu Agency )

LONDON, UNITED KINGDOM - DECEMBER 04: President of France Emmanuel Macron (L) is welcomed by British Prime Minister Boris Johnson (R) and NATO Secretary-General Jens Stoltenberg (C) during the NATO Summit in London, United Kingdom on December 4, 2019. ( Mustafa Kamacı - Anadolu Agency )

LONDON, UNITED KINGDOM - DECEMBER 04: President of France Emmanuel Macron (C) poses with British Prime Minister Boris Johnson (R) and NATO Secretary-General Jens Stoltenberg (L) during the NATO Summit in London, United Kingdom on December 4, 2019. ( Mustafa Kamacı - Anadolu Agency )

LONDON, UNITED KINGDOM - DECEMBER 4: British Prime Minister Boris Johnson (R) and Nato Secretary General Jens Stoltenberg (L) during the NATO Summit in London on 04 December 2019. ( Mustafa Kamaci - Anadolu Agency )

LONDON, UNITED KINGDOM - DECEMBER 4: British Prime Minister Boris Johnson (R) and Nato Secretary General Jens Stoltenberg (L) during the NATO Summit in London on 04 December 2019. ( Mustafa Kamaci - Anadolu Agency )