People hold a banner as they take part in an anti-Russian demonstration outside the Russian embassy, amid Russia's invasion of Ukraine, in Warsaw, Poland, April 13, 2022. The banner reads: "NATO! We demand to close the sky in Ukraine! Save children lives!" REUTERS/Aleksandra Szmigiel 

A member of the U.S. Navy operates onboard aircraft carrier USS Harry S. Truman, in the Adriatic Sea, February 2, 2022. The Truman strike group is operating under NATO command and control along with several other NATO allies for coordinated maritime manoeuvres, anti-submarine warfare training and long-range training. REUTERS/Yara Nardi 

Navy aviators operate onboard aircraft carrier USS Harry S. Truman, in the Adriatic Sea, February 2, 2022. The Truman strike group is operating under NATO command and control along with several other NATO allies for coordinated maritime manoeuvres, anti-submarine warfare training and long-range training. REUTERS/Yara Nardi 

U.S. Navy sailors operate onboard aircraft carrier USS Harry S. Truman, in the Adriatic Sea, February 2, 2022. The Truman strike group is operating under NATO command and control along with several other NATO allies for coordinated maritime manoeuvres, anti-submarine warfare training and long-range training. REUTERS/Yara Nardi 

A member of the U.S. Navy operates onboard aircraft carrier USS Harry S. Truman, in the Adriatic Sea, February 2, 2022. The Truman strike group is operating under NATO command and control along with several other NATO allies for coordinated maritime manoeuvres, anti-submarine warfare training and long-range training. REUTERS/Yara Nardi 

A Navy pilot operates onboard aircraft carrier USS Harry S. Truman, in the Adriatic Sea, February 2, 2022. The Truman strike group is operating under NATO command and control along with several other NATO allies for coordinated maritime manoeuvres, anti-submarine warfare training and long-range training. REUTERS/Yara Nardi 

A Navy pilot operates onboard aircraft carrier USS Harry S. Truman, in the Adriatic Sea, February 2, 2022. The Truman strike group is operating under NATO command and control along with several other NATO allies for coordinated maritime manoeuvres, anti-submarine warfare training and long-range training. REUTERS/Yara Nardi 

Members of the U.S. Navy attend a press conference onboard the aircraft carrier USS Harry S. Truman, in the Adriatic Sea, February 2, 2022. The Truman strike group is operating under NATO command and control along with several other NATO allies for coordinated maritime manoeuvres, anti-submarine warfare training and long-range training. REUTERS/Yara Nardi 

A military plane lands onboard aircraft carrier USS Harry S. Truman, in the Adriatic Sea, February 2, 2022. The Truman strike group is operating under NATO command and control along with several other NATO allies for coordinated maritime manoeuvres, anti-submarine warfare training and long-range training. REUTERS/Yara Nardi 

A general view of the aircraft carrier USS Harry S. Truman, in the Adriatic Sea, February 2, 2022. The Truman strike group is operating under NATO command and control along with several other NATO allies for coordinated maritime manoeuvres, anti-submarine warfare training and long-range training. REUTERS/Yara Nardi 

U.S. Navy sailors operate onboard aircraft carrier USS Harry S. Truman, in the Adriatic Sea, February 2, 2022. The Truman strike group is operating under NATO command and control along with several other NATO allies for coordinated maritime manoeuvres, anti-submarine warfare training and long-range training. REUTERS/Yara Nardi 

Members of U.S. Navy talk to each other on a military plane directs onboard the aircraft carrier USS Harry S. Truman, in the Adriatic Sea, February 2, 2022. The Truman strike group is operating under NATO command and control along with several other NATO allies for coordinated maritime manoeuvres, anti-submarine warfare training and long-range training. REUTERS/Yara Nardi 

A military plane F/A-18 lands onboard aircraft carrier USS Harry S. Truman, in the Adriatic Sea, February 2, 2022. The Truman strike group is operating under NATO command and control along with several other NATO allies for coordinated maritime manoeuvres, anti-submarine warfare training and long-range training. REUTERS/Yara Nardi TPX IMAGES OF THE DAY 

A general view of the aircraft carrier USS Harry S. Truman, in the Adriatic Sea, February 2, 2022. The Truman strike group is operating under NATO command and control along with several other NATO allies for coordinated maritime manoeuvres, anti-submarine warfare training and long-range training. REUTERS/Yara Nardi 

A member of U.S. Navy operates onboard aircraft carrier USS Harry S. Truman, in the Adriatic Sea, February 2, 2022. The Truman strike group is operating under NATO command and control along with several other NATO allies for coordinated maritime manoeuvres, anti-submarine warfare training and long-range training. REUTERS/Yara Nardi 

A general view of the aircraft carrier USS Harry S. Truman, in the Adriatic Sea, February 2, 2022. The Truman strike group is operating under NATO command and control along with several other NATO allies for coordinated maritime manoeuvres, anti-submarine warfare training and long-range training. REUTERS/Yara Nardi 

A U.S. Navy sailor operates onboard aircraft carrier USS Harry S. Truman, in the Adriatic Sea, February 2, 2022. The Truman strike group is operating under NATO command and control along with several other NATO allies for coordinated maritime manoeuvres, anti-submarine warfare training and long-range training. REUTERS/Yara Nardi 

Rear Admiral Curt Renshaw, commander of the Carrier Strike Group 8, speaks during a press conference onboard the aircraft carrier USS Harry S. Truman, in the Adriatic Sea, February 2, 2022. The Truman strike group is operating under NATO command and control along with several other NATO allies for coordinated maritime manoeuvres, anti-submarine warfare training and long-range training. REUTERS/Yara Nardi 

A member of U.S. Navy looks on a military plane onboard the aircraft carrier USS Harry S. Truman, in the Adriatic Sea, February 2, 2022. The Truman strike group is operating under NATO command and control along with several other NATO allies for coordinated maritime manoeuvres, anti-submarine warfare training and long-range training. REUTERS/Yara Nardi 

U.S. Navy sailors operate onboard aircraft carrier USS Harry S. Truman, in the Adriatic Sea, February 2, 2022. The Truman strike group is operating under NATO command and control along with several other NATO allies for coordinated maritime manoeuvres, anti-submarine warfare training and long-range training. REUTERS/Yara Nardi TPX IMAGES OF THE DAY 

A military plane lands onboard aircraft carrier USS Harry S. Truman, in the Adriatic Sea, February 2, 2022. The Truman strike group is operating under NATO command and control along with several other NATO allies for coordinated maritime manoeuvres, anti-submarine warfare training and long-range training. REUTERS/Yara Nardi 

A member of U.S. Navy operates onboard aircraft carrier USS Harry S. Truman, in the Adriatic Sea, February 2, 2022. The Truman strike group is operating under NATO command and control along with several other NATO allies for coordinated maritime manoeuvres, anti-submarine warfare training and long-range training. REUTERS/Yara Nardi 

Tactics schemes, that have been drawn on bridge windows of an Italian frigate Carabiniere F593, are seen during a NATO anti-submarine warfare exercise known as Dynamic Manta 2020, at sea off the coast of Catania, Italy, February 24, 2020. February 24, 2020. REUTERS/Antonio Parrinello 

Italian Navy soldiers are seen operating a Carabiniere F593 frigate, during a NATO anti-submarine warfare exercise known as Dynamic Manta 2020, at sea off the coast of Catania, Italy, February 24, 2020. Picture taken February 24, 2020. REUTERS/Antonio Parrinello 

An Italian Navy crew member prepares a Hydra SH90 helicopter on board of an Italian frigate Carabiniere F593, during a NATO anti-submarine warfare exercise known as Dynamic Manta 2020, at sea off the coast of Catania, Italy, February 24, 2020. Picture taken February 24, 2020. REUTERS/Antonio Parrinello 

An Italian Navy soldier is seen on board of a Carabiniere F593 frigate, during a NATO anti-submarine warfare exercise known as Dynamic Manta 2020, at sea off the coast of Catania, Italy, February 24, 2020. Picture taken February 24, 2020. REUTERS/Antonio Parrinello 

Italian Navy soldiers carry out out a disembarkment operation organised for the media, during a NATO anti-submarine warfare exercise known as Dynamic Manta 2020, at sea off the coast of Catania, Italy, February 24, 2020. Picture taken February 24, 2020. REUTERS/Antonio Parrinello 

A firefighter on board of an Italian frigate Carabiniere F593 is seen during a simulation of a fire extinguishing intervention, during a NATO anti-submarine warfare exercise known as Dynamic Manta 2020, at sea off the coast of Catania, Italy, February 24, 2020. Picture taken February 24, 2020. REUTERS/Antonio Parrinello 

Firefighters on board of an Italian frigate Carabiniere F593 simulate a fire extinguishing intervention, during a NATO anti-submarine warfare exercise known as Dynamic Manta 2020, at sea off the coast of Catania, Italy, February 24, 2020. Picture taken February 24, 2020. REUTERS/Antonio Parrinello 

An Italian Navy soldier carries out a disembarking operation organised for the media during a NATO anti-submarine warfare exercise known as Dynamic Manta 2020, at sea off the coast of Catania, Italy, February 24, 2020. Picture taken February 24, 2020. REUTERS/Antonio Parrinello 

Italian frigate Carabiniere F593 is seen at sea, during a NATO anti-submarine warfare exercise known as Dynamic Manta 2020, off the coast of Catania, Italy, February 24, 2020. Picture taken February 24, 2020. REUTERS/Antonio Parrinello 

U.S. Navy Rear Admiral Andrew Burcher (L) and Commander of the Standing NATO Maritime Group Two (SNMG2), Rear Admiral Paolo Fantoni (R), hold a news conference on board an Italian frigate during a NATO anti-submarine warfare exercise known as Dynamic Manta 2020, at sea off the coast of Catania, Italy, February 24, 2020. Picture taken February 24, 2020. REUTERS/Antonio Parrinello 

Italian Hydra SH90 helicopter is seen flying over the Canadian frigate HMCS Fredericton, during a NATO anti-submarine warfare exercise known as Dynamic Manta 2020, at sea off the coast of Catania, Italy, February 24, 2020. Picture taken February 24, 2020. REUTERS/Antonio Parrinello 

Italian submarine Todaro is seen partly submerged in water, during a NATO anti-submarine warfare exercise known as Dynamic Manta 2020, at sea off the coast of Catania, Italy, February 24, 2020. Picture taken February 24, 2020. REUTERS/Antonio Parrinello 

NATO's Centre for Maritime Research and Experimentation (CMRE) Director Catherine Warner is seen through glass, on board of an Italian frigate Carabiniere F593, during a NATO anti-submarine warfare exercise known as Dynamic Manta 2020, at sea off the coast of Catania, Italy, February 24, 2020. Picture taken February 24, 2020.REUTERS/Antonio Parrinello 

Italian Navy soldiers operate the Italian frigate Carabiniere F593 during a NATO anti-submarine warfare exercise known as Dynamic Manta 2020, at sea off the coast of Catania, Italy, February 24, 2020. Picture taken February 24, 2020. REUTERS/Antonio Parrinello 

Italian Navy soldiers are seen preparing the ?Romei? submarine, as part of a NATO anti-submarine warfare exercise known as Dynamic Manta 2020, in Catania, Italy, February 24, 2020. Picture taken February 24, 2020.REUTERS/Antonio Parrinello 

Italian Navy soldiers are seen preparing the ?Romei? submarine, as part of a NATO anti-submarine warfare exercise known as Dynamic Manta 2020, in Catania, Italy, February 24, 2020. Picture taken February 24, 2020.REUTERS/Antonio Parrinello 

Cockpit instruments are seen on board a "Atlantique 2" plane during a NATO anti-submarine warfare exercise known as Dynamic Manta 2020, at night in air off the coast of Catania, Italy, February 25, 2020. Picture taken February 25, 2020. REUTERS/Antonio Parrinello 

French Air Force pilots are seen operating "Atlantique 2" plane during a NATO anti-submarine warfare exercise known as Dynamic Manta 2020, in air off the coast of Catania, Italy, February 25, 2020. Picture taken February 25, 2020. REUTERS/Antonio Parrinello 

French Air Force pilots are seen operating an “Atlantique 2” airplane during a NATO anti-submarine warfare exercise known as Dynamic Manta 2020, in air off the coast of Catania, Italy, February 25, 2020. Picture taken February 25, 2020. REUTERS/Antonio Parrinello 

A French Air Force operator is seen by a circular rear window on board of "Atlantique 2" plane during a NATO anti-submarine warfare exercise known as Dynamic Manta 2020, in air off the coast of Catania, Italy, February 25, 2020. Picture taken February 25, 2020. REUTERS/Antonio Parrinello 

A French Air Force operator is seen by a circular rear window on board of "Atlantique 2" plane during a NATO anti-submarine warfare exercise known as Dynamic Manta 2020, in air off the coast of Catania, Italy, February 25, 2020. Picture taken February 25, 2020. REUTERS/Antonio Parrinello 

French Air Force operators are seen tracking a submarine on board of “Atlantique 2” airplane during a NATO anti-submarine warfare exercise known as Dynamic Manta 2020, in air off the coast of Catania, Italy, February 25, 2020. Picture taken February 25, 2020. REUTERS/Antonio Parrinello 

A French Air Force pilot is seen preparing sonobuoys on board an “Atlantique 2” airplane during a NATO anti-submarine warfare exercise known as Dynamic Manta 2020, in air off the coast of Catania, Italy, February 25, 2020. Picture taken February 25, 2020. REUTERS/Antonio Parrinello 

A French Air Force operator is seen searching for a submarine from a window of an “Atlantique 2” plane during a NATO anti-submarine warfare exercise known as 'Dynamic Manta 2020', in air off the coast of Catania, Italy, February 25, 2020. REUTERS/Antonio Parrinello 

Anti-Trump protestors outside Buckingham Palace ahead of the NATO summit in London, Britain December 3, 2019. REUTERS/Kevin Coombs 

The police control pro and anti-Trump protesters outside Buckingham Palace, ahead of the NATO summit in London, Britain December 3, 2019. REUTERS/Kevin Coombs 

The police control pro and anti Trump protesters outside Buckingham Palace, ahead of the NATO summit in London, Britain December 3, 2019. REUTERS/Kevin Coombs 

The police control pro and anti-Trump protesters outside Buckingham Palace ahead of the NATO summit in London, Britain December 3, 2019. REUTERS/Kevin Coombs 

The police control pro and anti-Trump supporters outside Buckingham Palace, ahead of the NATO summit in London, Britain December 3, 2019. REUTERS/Kevin Coombs 

Activist Danny Tommo is taken away by police after scuffles between pro and anti Trump supporters outside Buckingham Palace ahead of the NATO summit in London, Britain December 3, 2019. REUTERS/Kevin Coombs 

Danny Tommo, a well known activist, is taken away by police after scuffles between pro and anti Trump supporters outside Buckingham Palace ahead of the NATO summit, in London, Britain December 3, 2019. REUTERS/Dylan Martinez 

Danny Tommo, a well known activist, is taken away by police after scuffles between pro and anti Trump supporters outside Buckingham Palace ahead of the NATO summit, in London, Britain December 3, 2019. REUTERS/Dylan Martinez 

FILE PHOTO: A rebel fighter mans an anti-aircraft machine gun atop a pick-up truck as he scans the sky for NATO planes over the front-line along the western entrance of Ajdabiyah, Libya, April 14, 2011. REUTERS/Yannis Behrakis/File photo SEARCH "YANNIS BEHRAKIS" FOR THIS STORY. SEARCH "WIDER IMAGE" FOR ALL STORIES. 

Anti-NATO protestors hold a banner with the message "NATO refugees blood bombs death tears" during events organized by the government in 15 towns to celebrate an invitation for Macedonia to join NATO, in Skopje, Macedonia July 14, 2018. REUTERS/Ognen Teofilovski 

Anti-NATO protestors hold a banner with the message "NATO refugees blood bombs death tears" during events organized by the government in 15 towns to celebrate an invitation for Macedonia to join NATO, in Skopje, Macedonia July 14, 2018. REUTERS/Ognen Teofilovski 

Anti-EU protesters burn European Union and NATO flags during a demonstration in Sofia, Bulgaria, January 11, 2018. REUTERS/Stoyan Nenov