SZCZECIN, Poland

NATO's new rapid-reaction "spearhead" force, meant as a deterrent to Russian aggression, should be up and running with initial capabilities in less than a year, a top alliance official said Thursday.

The creation of a 4,000 to 5,000 troop response force, which will be able to respond to a crisis in eastern Europe within two to three days, was a key decision taken by NATO leaders earlier this month in Wales.

The force represents a calculation by NATO that Russian President Vladimir Putin won't risk going head-to-head with the Western alliance.

Deputy Secretary General Alexander Vershbow, the highest-ranking U.S. civilian at NATO, told The Associated Press on the sidelines of a symposium in Poland that military planners were now "working seven days a week" to finalize details of the force.

Those details should be in place to be approved by at defense ministers meeting in February, and implementation will move quickly ahead after that, he said.

"There's an expectation we will have at least an initial capacity with this much more rapid response time in less than a year from the Wales summit," he said. "It won't be all finished, but we recognize that the threats are here, we can't put this on the slow track."

Meanwhile, NATO's Multinational Corps Northeast headquarters, where the symposium was being held, is being upgraded to a "high readiness" force headquarters under the guidance of Germany, Poland and Denmark as part of the moves being made to reassure allies.

Russia seized the Crimean Peninsula from Ukraine earlier this year, and signs indicate that it has been funneling troops, tanks and artillery to the pro-Moscow separatists who have been fighting government forces in eastern Ukraine over the past five months.

Ukraine is not a NATO member and not directly under its defense umbrella, but three other former Soviet republics have joined the alliance since the end of the Cold War, as well as the former Soviet satellite states of Poland, Hungary, the Czech Republic and Slovakia, Romania and Bulgaria.

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NATO to fast-track rapid-reaction force to deter Russia