NATO said today it will deploy additional air, sea and land forces in eastern Europe in response to the worsening crisis in Ukraine and will take further action if needed.
"Today we have agreed a package of military measures," NATO head Anders Fogh Rasmussen said after a meeting of ambassadors of all 28 members of the transatlantic alliance.
"We will have more planes in the air, more ships on the water... And more readiness on the land," he said, adding that NATO defence plans will be "reviewed and reinforced".
The announcement came as Ukrainian and pro-Russian forces faced off and after President Vladimir Putin warned the country was on the brink of civil war, stoking fears of outright Russian intervention.
Rasmussen refused to detail what new forces would be deployed and where, but said they would result in increased air sorties over the Baltic Sea, with additional ships there and in the eastern Mediterranean.
The decision will be implemented "immediately" and "more will follow, if needed, in the weeks and months to come," he added.
As the Ukraine crisis has unfolded, NATO has taken a number of similar steps, with the United States sending fighter aircraft to the Baltic states and Poland to bolster confidence in member countries once ruled by Moscow.
Estonia, Latvia and Lithuania -- which border Russia and have sizeable ethnic Russian populations -- have all sought reassurance, as have Ukraine neighbours Poland and Romania.
Freed from Moscow's Cold War rule with the fall of Communism in the late 1980s, many eastern Europe states have readily joined NATO.
But Russia, especially under Putin, has regarded NATO's eastward expansion as a direct security threat.
The former Soviet states "are increasingly worried as they see the crisis getting worse by the hour," said one diplomat.
"So far, NATO's response has been measured," said another diplomat, noting that the allies had not put troops on the ground, set up bases or increased their presence in the Black Sea.
Rasmussen stressed NATO would stand by any ally against any threat, and that the measures announced were entirely in keeping with international law and the alliance's commitment to deterrence.
Asked about calls for permanent bases in the Baltic states, he said the issue was not discussed at the meeting.
There "will be follow-on work" to the steps now taken, he said, adding the alliance continued "exploring ways to possibly further enhance our collective defence."
He also repeated calls for Russia "to be part of the solution, to stop destabilising Ukraine, pull back its troops from the borders and make clear it does not support the violent actions of well-armed militias of pro-Russian separatists.
