By Adrian Croft and Michael Holden
NEWPORT Wales (Reuters) - 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 alliance in the last 15 years, especially Poland and the Baltic states of Estonia, Latvia and Lithuania.
Bowing to U.S. pressure, the leaders pledged to stop a sharp slide in military spending, exacerbated by the financial crisis, that Washington says has severely weakened European allies' defense capabilities.
Low-spending NATO members pledged to avoid any more cuts in defense spending and to increase it towards NATO's guideline of 2 percent of economic output - although only within a decade.
The alliance 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.
U.S. President Barack Obama said that, in light of recent Russian actions and rhetoric, the plan was intended to make it crystal clear that NATO's mutual self-defense commitment meant what it said.
"An increased presence serves as the most effective deterrent to any additional Russian aggression that we might see," he told a news conference at the end of the summit at the Celtic Manor resort in south Wales.
Central to NATO's plans is the new "spearhead" rapid reaction force, expected to consist of up to 5,000 ground troops with air, sea and special forces support.
The first units of the force will be ready to move in two days, compared with the five needed by NATO's current response force. The troops will be drawn from existing units when needed.
NATO, refocusing on its core mission of defending Europe and North America after more than a decade of combat operations in Afghanistan, will also step up exercises in eastern Europe and continue to rotate air, sea and land forces through the region.
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.
"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," NATO Secretary-General Anders Fogh Rasmussen told a news conference.
Polish Prime Minister Donald Tusk said the decision showed that security guarantees for Warsaw were no longer just paper promises but for real. Poland also said it would host the next NATO summit in 2016.
British Prime Minister David Cameron said Britain would contribute 3,500 personnel to exercises in eastern Europe between now and the end of 2015 as part of NATO's effort to ensure a "persistent presence" on its eastern flank.
Britain will also provide a battlegroup and a brigade headquarters for the new rapid reaction force, he said.
NATO's military planners still have to put meat on the bones of the plan. A top NATO commander, British Gen. Adrian Bradshaw, said it could take a number of months, maybe a year, for the spearhead force to begin operating.
A unanimous political decision by all 28 NATO allies would also be needed to order the rapid reaction force into action, which could undermine any move to deploy it quickly if any ally objected to its use.
Although no final decisions have been taken, Szczecin in Poland could be chosen as a new "headquarters for collective defense" in the region, NATO officials said. The headquarters, which has a staff of around 200 Poles, Germans and Danes is being doubled in size to 400.
Russia said joint military exercises planned by Kiev and the United States in Ukraine this month and NATO rhetoric could undermine peace moves in the former Soviet republic.
NATO's pledge to gradually increase defense spending was a hard-fought compromise. But Italy immediately raised questions, with Prime Minister Matteo Renzi saying any extra outlays on defense should be exempted from European Union rules limiting budget deficits. Italy spent the equivalent of 1.2 percent of GDP in 2013, according to NATO figures.
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 led NATO to abandon, for now, attempts to strike up a partnership with its erstwhile Cold War foe.
While NATO leaders talked, fighting raged between Ukrainian forces and pro-Russian rebels near the port of Mariupol, minutes before envoys from Ukraine, Russia and the rebels agreed in Minsk on a ceasefire and a peace plan.
Allies in the Baltics fear 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 the Baltics, 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.
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 agreed on measures, including advice on armed forces reform, that Rasmussen said would help Georgia advance in its preparations towards eventual membership of the group. In June NATO foreign ministers had 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 no third country had a veto over NATO enlargement, a reference to Moscow's warnings against Ukraine's bid to join. But key European allies including France and Germany remain opposed to Kiev joining, saying it would be a provocation to Russia and could suck the alliance into a war.
With combat operations in Afghanistan due to end this year, NATO wants to keep close ties with non-NATO member countries that participated in its operations there and elsewhere.
NATO invited 24 countries to cooperate with the alliance on military issues while five countries - Australia, Finland, Georgia, Jordan and Sweden - were offered an even closer level of political and military cooperation.
(Additional reporting by Paul Taylor, Guy Faulconbridge, Steve Holland, Phil Stewart, Sabine Siebold, Kylie Maclellan, Gavin Jones; Editing by Hugh Lawson)