NATO leaders vowed Monday to stand by Afghanistan as it takes control of its own destiny, backing a plan to hand Afghans the lead for security in the war-torn country from mid-2013.

In a Chicago summit declaration, US President Barack Obama and his NATO military allies ratified an "irreversible" roadmap to "gradually and responsibly" withdraw 130,000 combat troops by the end of 2014.

But they also ordered military officers to begin planning a post-2014 mission to focus on training, advising and assisting Afghan troops to ensure the government can ward off a resilient Taliban insurgency.

"As Afghans stand up, they will not stand alone," Obama told the gathering of more than 50 world leaders, focused on ending a decade of war that has left over 3,000 coalition soldiers and tens of thousands of Afghans dead.

British Prime Minister David Cameron, whose country provides the second biggest contingent after the United States, declared: "We will not desert them."

But while the Western alliance coalesced around an exit strategy, they struggled to convince Pakistan to reopen a vital supply route into Afghanistan, although NATO chief Anders Fogh Rasmussen voiced optimism it would happen "in the very near future."

The 28 NATO leaders and their 22 partners in the war, as far afield as Australia, Georgia and South Korea, issued a final statement saying Afghans will be in "lead for security nationwide" by mid-2013.

Though NATO troops will gradually shift focus to training and support, alliance officials stressed that foreign soldiers would still participate in combat operations when needed until late 2014.

The two-day summit gave Obama a platform to show a war-weary American public that he has global support for his plan to end the war ahead of a tough re-election campaign against Republican Mitt Romney in November.

Chicago was under tight security as thousands of people protested during the summit, with arrests and scenes of clashes between anti-war demonstrators and riot police on Sunday.

The carefully-crafted Afghanistan strategy had appeared on shaky ground when new French President Francois Hollande decided to speed up his country's withdrawal to this year, but the alliance secured a French pledge for a training mission.

With the Taliban still resilient after a decade of war, NATO leaders sought to reassure Afghan President Hamid Karzai that the international community would not abandon his country after combat troops are gone.

The 50 nations involved in the war endorsed a US plan to provide $4.1 billion in annual security aid to Afghanistan and reduce the size of Afghan forces from a peak of 352,000 to 228,500.

The United States has offered to pay half the bill while the international community is expected to stump up the rest. But the summit declaration makes clear that the security aid will not last forever.

The declaration says the Afghan government's share of the bill will increase progressively from $500 million in 2015, "with the aim that it can assume, no later than 2024, full financial responsibility for its own security forces."

Although the Taliban insurgency remains resilient, NATO officials say the size of the Afghan army can be reduced after 2014 because they expect the security situation to improve.

The 28 allies, who discussed Afghanistan over dinner at the American football Soldier Field late Sunday, met Monday with some 30 world leaders including Pakistani President Asif Ali Zardari.

Zardari's attendance had raised hopes his government was ready to lift a blockade on NATO convoys, but talks on reopening the routes have stumbled over Islamabad's demand to charge steep fees for trucks crossing the border.

In their declaration, the NATO leaders said it was still working with Pakistan to reopen the border crossing, which was used to bring fuel and other supplies to foreign troops, "as soon as possible."

Zardari told the NATO leaders that Pakistani officials had been told to reach an agreement to reopen the supply routes, closed in November after a botched US air raid that left 24 Pakistani soldiers dead.

To ferry troops, food and equipment into Afghanistan, the US-led force in Afghanistan has relied on cargo flights and a more costly northern route network that passes through Russia, Central Asia and the Caucasus.