NATO approved wide-ranging plans on Friday to boost its defenses in eastern Europe, aiming to reassure allies nervous about Russia's intervention in Ukraine that the U.S.-led alliance will shield them from any attack.

The plan, adopted at a summit in Wales, includes creating a "spearhead" rapid reaction force and pre-positioning supplies and equipment in east European countries so they can be reinforced within days in a crisis.

The initiative was intended to provide assurances to former Soviet bloc states that have joined the U.S.-led the alliance in the last 15 years, especially Poland and the Baltic states of Estonia, Latvia and Lithuania.

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The 28-nation alliance also agreed for the first time to add cyber defense to its core mission, meaning that a major cyber attack on a member state - such as a 2007 attack on Estonia's digital infrastructure - could trigger a military response.

NATO Secretary-General Anders Fogh Rasmussen said the new spearhead force would include several thousand ground troops, ready to deploy within a few days with air, sea and special forces support.

While that falls short of the permanent NATO bases Poland and other eastern countries wanted, it will ensure a NATO presence that would deter an aggressor by acting as a trip wire that, if crossed, could trigger a full-scale military response from the U.S. and its allies.

Polish Prime Minister Donald Tusk said the decision sent a clear signal that security guarantees for Warsaw were no longer just paper promises but for real.

"This decision sends a clear message: NATO protects all allies, at all times. And it sends a clear message to any potential aggressor: Should you even think of attacking one ally, you will be facing the whole alliance," Rasmussen told a news conference.

STRATEGY OVERHAUL

Russia's annexation of Ukraine's Crimea region in March as well as what NATO says is a direct Russian military intervention in support of pro-Russian separatists in eastern Ukraine has triggered a complete overhaul of NATO's strategy towards Russia after years in which the alliance had tried to strike up a partnership with its erstwhile Cold War foe.

While U.S. President Barack Obama and other leaders met at a scenic golf resort in Wales, fighting raged between Ukrainian forces and pro-Russian rebels just east of the strategic port of Mariupol on Friday, minutes before envoys from Ukraine, Russia and the rebels agreed in Minsk on a ceasefire and a peace plan.

Polish President Bronislaw Komorowski announced that his country would host the next NATO summit in 2016.

The first units of the rapid reaction force expected to total about 5,000 troops will be ready to move in two days, compared to the five needed by NATO's current response force. The troops will be drawn from existing units when needed.

NATO will also step up exercises in eastern Europe and continue to rotate air, sea and land forces through the region.

Allies in the Baltics fear that Russian President Vladimir Putin could use the same rationale as he used to explain intervention in Crimea - defending Russian speakers - to justify an attack against one of the NATO countries in theBaltics, which also have Russian-speaking minorities.

NATO is also revising its strategy to deal with the "hybrid" tactics used by Russia in Ukraine - including the use of soldiers without national markings, cyber attacks and disinformation campaigns.

CYBER DEFENSE

The decision on cyber defense marks a significant expansion of the organization's remit, reflecting new threats that can disable critical infrastructure, financial systems and government without firing a shot.

"We agree that cyber attacks can reach a level that threatens the prosperity, security and stability of our countries ... They could harm our modern societies as much as a conventional attack. So today, we declare that cyber defense is part of NATO’s core task of collective defense," Rasmussen said.

In 2007, a series of crippling cyber attacks paralyzed much of NATO member Estonia in an apparent response to a dispute over the movement of a Soviet-era war memorial. Most Western experts suspected the Kremlin was responsible but Russia denied it.

NATO leaders were expected to agree later on Friday to aim to reach the alliance's goal of spending the equivalent of two percent of their economic output on defense within the next decade, and to stop a slide in defense spending that the United States say has dangerously weakened the alliance.

They also agreed on a package of measures, including advice on reforming its armed forces, that Rasmussen said would help Georgia advance in its preparations towards eventual membership of NATO.

The package is a consolation prize after NATO foreign ministers in June dashed Georgia's hopes of being given a formal step towards NATO accession, known as a membership action plan.

Georgian hopes of joining NATO were set back by a brief war with Russia in 2008.

Rasmussen insisted that no third country had a veto over NATO's enlargement, a reference to Moscow's warnings against Ukraine's bid to join the alliance. However, key European allies including France and Germany remain opposed to bringing Kiev into NATO, arguing that it would be a provocation to Russia and could suck the alliance into a war.