On Tuesday, sparked by the presence of two US warships, Russia’s Black Sea naval forces practised destroying enemy targets at its bases in Novorossiysk and on Crimea, the peninsula it annexed from Ukraine in 2014.
The US Navy said the USS Mount Whitney had arrived in Istanbul and would shortly join forces with other ships in the Black Sea “to further enhance collaboration between US and NATO forces at sea”.
Meanwhile, Politico reported that commercial satellite photos taken on Monday confirmed recent reports that Russia is once more massing troops and military equipment on the border with Ukraine after a major build-up this spring.
A NATO official said: “NATO is vigilant and routinely monitors Russian force movements.
“It’s important to ensure transparency and avoid any miscalculation.”
Moscow last month announced it planned to cease its diplomatic engagement with NATO.
Though no military moves followed the announcement, the decisions worsened the already fragile ties of the alliance with Russia.
Since Moscow’s annexation of Crimea — Russia considers Crimea part of its territory but the peninsula is internationally recognised as part of Ukraine — NATO is particularly wary of protecting the security of its member states, especially those near Russia.
Moscow’s backing for pro-Russian rebels in eastern Ukraine has also added to the alliance’s determination to reinforce security.