WARSAW — NATO leaders meet on Friday for a landmark summit in Warsaw to send an uncompromising message to a resurgent Russia while trying to contain the fallout from Britain’s dramatic vote to quit the European Union.

Britain’s divorce from the EU is set to dominate talks between US President Barack Obama, attending his last NATO summit, and EU President Donald Tusk and European Commission chief Jean-Claude Juncker.

The uncertainty over a key nuclear-armed ally comes as NATO prepares to green-light its biggest revamp since the end of the Cold War in the face of fears sparked by Russia’s 2014 intervention in Ukraine.

Security is tight across the Polish capital with police locking down key roads around the venue in Poland’s national stadium and helicopters flying overhead.

Charles Kupchan, who heads the Europe section in the US National Security Council, said the EU meeting would also "be an early opportunity for the president to discuss the implications of the British referendum".

With Britain being the largest EU military contributor to NATO, Obama will "weigh in on his views about how best to handle the prospect of (a Brexit) and what its economic and geopolitical implications might be", he said.

Obama will also meet British Prime Minister David Cameron at the summit, which gathers all 28 NATO members in Warsaw, where the Soviet Union put together the Warsaw Pact in 1955 to counter its adversary NATO.

US NATO ambassador Douglas Lute said the summit "comes at a real demarcation point, or an inflection point, in the now almost 70-year history of the Alliance".

From Warsaw Pact to NATO

The summit centrepiece is a "Readiness Action Plan" to bolster NATO resources and readiness in the face of a Russia under President Vladimir Putin that the allies now see as more aggressive and dangerously unpredictable.

NATO leaders will approve rotating four battalions in eastern Europe – in Poland, Estonia, Latvia and Lithuania, up to 4,000 troops in all -- to act as a tripwire against any fresh Russian adventurism.

Britain announced on Friday it would contribute 650 troops to Estonia and Poland.

The plan also includes a pledge to spend two percent of annual economic output on defence, ending years of cuts, and the creation of a 5,000-strong "Spearhead" force ready to deploy within days.

German Chancellor Angela Merkel said on Thursday that Russia’s actions in Ukraine had eroded mutual trust, adding that the summit comes "in a phase in which the security situation has significantly changed in Europe".

But she stressed the need for "deterrence and dialogue" with Moscow, echoing the tone from the White House on how to handle Putin’s Russia.

Russia, missile defence

Russia bitterly opposes NATO’s expansion into its Soviet-era satellites, which it sees as a threat to its own security.

However, Moscow reserves its direst warnings for the Ballistic Missile Defence system the United States is building and which the summit is due to declare has reached an initial operating level.

Washington says the shield is designed to counter missile threats from Iran or the Middle East but Russia says that once the system becomes fully operational in 2018, it will undercut its strategic nuclear deterrent.

NATO head Jens Stoltenberg announced this week that the alliance would hold fresh formal talks with Russia just after the summit.

Russia’s reading of the talks in the NATO-Russia Council was uncompromising, with Russian ambassador to NATO Alexander Grushko saying the "focus will be on the military security in the wake of decisions to be taken at the NATO summit in Warsaw".

The NATO leaders will discuss the deteriorating situation in Afghanistan where Obama on Wednesday said he would keep 8,400 troops into next year to tackle the Taliban, 15 years after allied forces invaded in the wake of the 9/11 attacks.

The summit meanwhile will also approve a NATO-EU cooperation accord, laying out how the alliance -- which includes 22 of the 28 EU member states – can work with the EU.

The EU has an embryonic security policy but mass migration and new terrorist threats emerging from failing states in the Middle East, North Africa and beyond are driving the 28-nation bloc to up its game. — AFP