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

Bar chart showing pro/anti NATO feeling

A participant wears a T-shirt with an image of Russian President Vladimir Putin during anti-NATO protest as Montenegro’s parliament discusses NATO membership agreement in Cetinje, Montenegro, April 28, 2017. REUTERS/Stevo Vasiljevic

Demonstrators wave flags during anti-NATO protest as Montenegro’s parliament discusses NATO membership agreement in Cetinje, Montenegro, April 28, 2017. REUTERS/Stevo Vasiljevic

Commander Maritime Air NATO Andreas Vettos attends a news conference during NATO's Dynamic Manta 2017 anti-submarine warfare exercise, in the Mediterranean sea, Italy March 13, 2017. Picture taken March 13, 2017. REUTERS/Antonio Parrinello

Commander Maritime Air NATO Andreas Vettos attends a news conference during NATO's Dynamic Manta 2017 anti-submarine warfare exercise, in the Mediterranean sea, Italy March 13, 2017. Picture taken March 13, 2017. REUTERS/Antonio Parrinello

A crew member of Spanish Navy frigate Mendez Nunez participate in NATO's Dynamic Manta 2017 anti-submarine warfare exercise, in the Mediterranean sea, Italy March 13, 2017. Picture taken March 13, 2017. REUTERS/Antonio Parrinello

A crew member of the Spanish Navy frigate Mendez Nunez participate in NATO's Dynamic Manta 2017 anti-submarine warfare exercise, in the Mediterranean sea, Italy March 13, 2017. Picture taken March 13, 2017. REUTERS/Antonio Parrinello

Crew of the Spanish Navy frigate Mendez Nunez participate in NATO's Dynamic Manta 2017 anti-submarine warfare exercise, in the Mediterranean sea, Italy March 13, 2017. Picture taken March 13, 2017. REUTERS/Antonio Parrinello

Crew of the Spanish Navy frigate Mendez Nunez participate in NATO's Dynamic Manta 2017 anti-submarine warfare exercise, in the Mediterranean sea, Italy March 13, 2017. Picture taken March 13, 2017. REUTERS/Antonio Parrinello

A crew member of Spanish Navy frigate Mendez Nunez participates in NATO's Dynamic Manta 2017 anti-submarine warfare exercise, in the Mediterranean sea, Italy March 13, 2017. Picture taken March 13, 2017. REUTERS/Antonio Parrinello

A crew member of Spanish Navy frigate Mendez Nunez participates in NATO's Dynamic Manta 2017 anti-submarine warfare exercise, in the Mediterranean sea, Italy March 13, 2017. Picture taken March 13, 2017. REUTERS/Antonio Parrinello

Submarines participate in NATO's Dynamic Manta 2017 anti-submarine warfare exercise, in the Mediterranean sea, Italy March 13, 2017. Picture taken March 13, 2017. REUTERS/Antonio Parrinello

Warships participate in NATO's Dynamic Manta 2017 anti-submarine warfare exercise, in the Mediterranean sea, Italy March 13, 2017. Picture taken March 13, 2017. REUTERS/Antonio Parrinello

French Navy Frigate Montcalm participates in NATO's Dynamic Manta 2017 anti-submarine warfare exercise, in the Mediterranean sea, Italy March 13, 2017. Picture taken March 13, 2017. REUTERS/Antonio Parrinello

Warships participate in NATO's Dynamic Manta 2017 anti-submarine warfare exercise, in the Mediterranean sea, Italy March 13, 2017. Picture taken March 13, 2017. REUTERS/Antonio Parrinello

Warships participate in NATO's Dynamic Manta 2017 anti-submarine warfare exercise, in the Mediterranean sea, Italy March 13, 2017. Picture taken March 13, 2017. REUTERS/Antonio Parrinello

Warships participate in NATO's Dynamic Manta 2017 anti-submarine warfare exercise, in the Mediterranean sea, Italy March 13, 2017. Picture taken March 13, 2017. REUTERS/Antonio Parrinello

Submarines are seen during NATO's Dynamic Manta 2017 anti-submarine warfare exercise, in Catania's harbour, southern Italy March 13, 2017. Picture taken March 13, 2017. REUTERS/Antonio Parrinello

Submarines are seen during NATO's Dynamic Manta 2017 anti-submarine warfare exercise, in Catania's harbour, southern Italy March 13, 2017. Picture taken March 13, 2017. REUTERS/Antonio Parrinello

U.S. submarine New Mexico is seen during NATO's Dynamic Manta 2017 anti-submarine warfare exercise, in Catania's harbour, southern Italy March 13, 2017. Picture taken March 13, 2017. REUTERS/Antonio Parrinello

U.S. submarine New Mexico is seen during NATO's Dynamic Manta 2017 anti-submarine warfare exercise, in Catania's harbour, southern Italy March 13, 2017. Picture taken March 13, 2017. REUTERS/Antonio Parrinello

Greek submarine Papanikolis is seen during NATO's Dynamic Manta 2017 anti-submarine warfare exercise, in Catania's harbour, southern Italy March 13, 2017. Picture taken March 13, 2017. REUTERS/Antonio Parrinello

Momir Bulatovic, who was the Yugoslavian prime minister during NATO's 1999 bombing campaign, speaks during an anti-NATO protest in Podgorica, Montenegro, December 12, 2015. REUTERS/Stevo Vasiljevic

Momir Bulatovic, who was the Yugoslavian prime minister during NATO's 1999 bombing campaign, speaks during an anti-NATO protest in Podgorica, Montenegro, December 12, 2015. REUTERS/Stevo Vasiljevic