The United States called on Russia to halt a military build-up on Ukraine's border yesterday as Moscow, in words recalling the Cold War, said its "adversary" should keep US warships well away from annexed Crimea.
Moscow seized Crimea from Ukraine in 2014 and fighting has escalated in recent weeks in eastern Ukraine, where government forces have battled Russian-backed separatists in a seven-year conflict that Kyiv says has killed 14,000 people.
Two US warships are due to arrive in the Black Sea this week.
In Brussels for talks with Nato leaders and Ukraine's foreign minister, US Secretary of State Antony Blinken said Washington stood firmly behind Ukraine. He also said he would discuss Kyiv's ambitions to one day join Nato - although France and Germany have long worried that bringing the former Soviet republic into the Western alliance would antagonise Russia.
"The United States is our adversary and does everything it can to undermine Russia's position on the world stage," Deputy Foreign Minister Sergei Ryabkov was quoted as saying by Russian news agencies on Tuesday.
Ryabkov's remarks suggest that the diplomatic niceties which the former Cold War enemies have generally sought to observe in recent decades is fraying, and that Russia would robustly push back against what it regards as unacceptable US interference in its sphere of influence.
"We warn the United States that it will be better for them to stay far away from Crimea and our Black Sea coast. It will be for their own good," Ryabkov said, calling the US deployment a provocation.
Russia has regularly accused Nato of destabilising Europe with its troop reinforcements in the Baltics and Poland since the annexation of Crimea.
Russian Defence Minister Sergei Shoigu said Russia had moved two armies and three paratrooper units to near its western borders in the last three weeks, responding to what it called threatening military action by Nato.