Moscow has bristled at a request from the Baltic states to have Nato troops based permanently on their territory, in response to rising fear of Russian aggression.
Latvia, Lithuania and Estonia announced their appeal as Nato and the European Union pledged to strengthen their defence against the kind of "hybrid warfare" that Moscow is accused of unleashing in Ukraine.
The Baltic countries, which were part of the Soviet Union and have sizeable ethnic Russian minorities, are expected to send a joint letter to Nato next week asking for a brigade to be deployed to the region, so that a battalion could be based in each country. A Nato brigade usually comprises some 3,000 to 5,000 soldiers.
Latvia's defence ministry said in a statement: "An allied presence is an essential prerequisite for Latvia's security in a situation where Russia does not change its policies regarding the Ukraine conflict and at the same time strongly demonstrates its military presence and potential in the Baltic Sea region."
At a meeting of Nato foreign ministers in Turkey, the alliance's secretary general, Jens Stoltenberg, said it would "go carefully through the letter and assess the proposals".
The Baltic countries have been rattled by the war in nearby Ukraine, where Russia last year annexed Crimea and fomented a separatist uprising in the east that has killed more than 6,100 people and displaced well over one million.
They have been further alarmed by a sharp increase in the number of Russian military aircraft and ships approaching their borders, although Moscow insists that Nato has also ramped up activity in the region.
Nato has also conducted major military exercises across central and eastern Europe, and Russia has done the same near Ukraine's border and in Kaliningrad, a Russian enclave with a large naval base sandwiched between Poland and Lithuania.
Poland is also “seeking Nato’s permanent regional presence” in the shape of “bases with heavy equipment”, according to a military planning document seen by Reuters.
Jets from fellow Nato states have long provided air defence for the Baltic states, and since last year about 150 US troops have been stationed in each of them and in Poland.
Vladimir Chizhov, Russia's ambassador to the EU, said the request to Nato was motivated by "local politics rather than a genuine security situation. Because nobody is threatening the Baltics – at least, nobody that I know of."