US President Barack Obama has arrived in Estonia on a visit apparently aimed at showing Washington’s solidarity with the three Baltic states, one day before a NATO summit in Wales, where Russia’s involvement in Ukraine is expected to be the main topic.

Obama will meet with the leaders of Estonia, Latvia and Lithuania later on Wednesday to offer reassurances to the three NATO member states located near the Russian border, following the alleged Russian-backed military offensive in Ukraine.

The Baltic states are seen by some as especially vulnerable to Moscow’s attention because of their Russian minorities and high dependence on energy shipments from their larger neighbour.

At the two-day summit in Wales, the Baltic states will press for some kind of deployment of NATO troops, in addition to increased air patrols already announced by the alliance this year.

NATO agreed this week to create a “spearhead” rapid reaction force, potentially including several thousand troops, that could be sent to a hot spot in as little as two days, down from an earlier response time of around five days.

But the miltary alliance remains divided on setting up permanent bases in the east.

Moscow revising defence policy

On Wednesday, a top Russian defence official said Moscow would adopt a new military doctrine over NATO’s expansion and the alliance’s plans to establish the rapid-response force in the wake of the rebellion in Ukraine’s east.

Russian Defence Minister Sergei Shoigu said in separate comments on Tuesday that Russia’s armed forces would be given added muscle with the deployment of 230 new helicopters and fighter jets by the end of the year.

Sergei Lavrov, the Russian foreign minister, said that Ukrainian moves to seek NATO membership were aimed at undermining efforts to end the war in the east of the country.

Anchored in NATO, unlike Ukraine, the three Baltic states have far less cause to fear a full-blown Russian military invasion, but they worry about cyberattacks and other more stealth-like forms of aggression. Al Jazeera