BRUSSELS - NATO was set Thursday to agree a major boost to the alliance's defences near its Russian borders, including six command centres and a quick-reaction spearhead force of 5,000 troops in response to the crisis in Ukraine.
Secretary General Jens Stoltenberg said ahead of a meeting of defence ministers in Brussels that the move was in response to Moscow's "aggressive actions," but nevertheless purely defensive.
"This is something we do as a response to the aggressive actions we have seen from Russia, violating international law and annexing Crimea," he told reporters as he arrived at the 28-nation group's headquarters.
The NATO defence ministers are expected to agree on a so-called "spearhead" force of around 5,000 troops which will be able to deploy anywhere within a "few days," Stoltenberg said.
They are also to finalise the list of the countries taking part in the force, which will is part of a wider NATO response force of 13,000 to 30,000 troops that would take weeks or months to deploy in a crisis.
In a move that is likely to irk Moscow, NATO will also decide on six "command and control" units in Eastern European nations to ensure that the new force could hit the ground running.
The bases will be in the three Baltic former Soviet states - Estonia, Latvia and Lithuania - plus Poland, Romania and Bulgaria, Stoltenberg has previously said.
"They will plan, organise exercises and they will be a key for connecting national forces with NATO reinforcements," the alliance chief said.
The multinational headquarters for the command and control centres will be in Szczecin, Poland, which will also be boosted, he said.
Stoltenberg said the NATO measures were also motivated by new threats from Islamist militants in North Africa and the Middle East who are fuelling violence within Europe.
The NATO chief said he would meet later this week on the sidelines of the Munich security conference with US Vice President Joe Biden, Ukrainian President Petro Poroshenko and Russia Foreign Minister Sergei Lavrov.
He said his talks with Lavrov are part of keeping political channels open with Russia after the alliance ended "practical cooperation" with Moscow over the Ukraine crisis.
The Western allies are still seeking a diplomatic solution to the crisis in Ukraine, where government forces have been fighting pro-Moscow rebels since April.