NATO leaders will respond to the Ukraine crisis by agreeing this week to create a "spearhead" rapid reaction force, potentially including several thousand troops, that could be sent to a hotspot in as little as two days, officials said on Monday.
The 28-nation alliance already has a rapid reaction force but U.S. President Barack Obama and other leaders meeting for a NATO summit in Wales on Thursday and Friday are expected to create a new force that would be able to respond more quickly to a crisis.
The speed with which Russian forces infiltrated Ukraine's Crimea region in March has focused minds at NATO on speeding up its ability to respond if a similar crisis ever occurred on NATO territory.
"We will develop what I would call a spearhead ... a very high-readiness force able to deploy at very short notice. This spearhead would be provided by allies in rotation, and could include several thousand troops, ready to respond where needed with air, sea and special forces support," NATO Secretary-General Anders Fogh Rasmussen told a news conference.
A senior NATO official, speaking on condition of anonymity, said the spearhead force could range from "a very small size up to something potentially as large as a brigade size". A NATO brigade typically numbers between 3,000 and 5,000 troops.
The official said the force would be able to deploy to a crisis zone in just two days. Other NATO sources said however that some elements of the force might take longer to arrive.
Currently it takes five days for the first units of NATO's rapid reaction force to arrive.
The creation of the new force will be one of a range of measures in a "readiness action plan" that NATO will adopt at the summit to step up deterrence in response to the Ukraine crisis.
Eastern European NATO members, including Poland, have appealed to NATO to permanently station thousands of troops on its territory to deter any possible Russian attack.
But NATO members have spurned that idea, partly because of the expense and partly because they do not want to break a 1997 agreement with Russia under which NATO committed not to permanently station significant combat forces in the east.
Instead NATO leaders will agree to pre-position equipment and supplies, such as fuel and ammunition, in eastern European countries with bases ready to receive the NATO rapid reaction force if needed,
This will enable the new rapid reaction force to "travel light, but strike hard if needed", Rasmussen said.
Infrastructure such as ports and airstrips in Poland and the Baltics may have to be upgraded to enable them to receive reinforcements quickly if needed, NATO officials say.
The goal of the NATO plan is to show that it is serious about its key commitment that an attack on one NATO member is considered an attack on all and that it would come to the aid of any NATO ally if it faced aggression.
NATO will continue with the short-term measures it put in place in response to the Ukraine crisis which include sending more fighter aircraft to the Baltics and stepping up military exercises in eastern Europe.
The "spearhead" force is different to a new "joint expeditionary force" that Britain and six other NATO allies plan to set up, NATO officials said.
"What the UK is doing ... is establishing this joint expeditionary force which could be used for NATO but could be used for other things as well, whether a European Union operation, a U.N. operation or indeed national operations," the senior NATO official said.
The British-led force could follow behind NATO's spearhead force in a crisis, he said.
NATO leaders will also "enhance the breadth and depth" of the naval forces it has on standby, which allies take turns to contribute to.
They will also work to improve alliance intelligence capabilities and its ability to respond to the type of "hybrid" warfare used by Russia in Ukraine, which NATO officials say have included disinformation, subversion and cyber attack.