US President Barack Obama said Sunday the world backed his plan to end the Afghan war in two years, as President Hamid Karzai promised a NATO summit his bloodied state would no longer be a "burden."

Leaders of the 28 NATO nations stood in solemn silence as a bugler's lament recalled the heavy cost of a conflict that has killed over 3,000 coalition soldiers, maimed thousands more and left tens of thousands of Afghans dead.

As war weary western publics pine for an exit, the two-day summit was set to endorse a withdrawal strategy and seek firm commitments from alliance states to train and bankroll Afghan forces to ensure a decade of sacrifice is not wasted.

Before the summit, Obama met Karzai three weeks after his dramatic flight into Kabul where the two leaders inked a security pact for going forward after the withdrawal of international troops in late 2014.

"We're confident that we are on the right track, and what this NATO Summit reflects is that the world is behind the strategy that we've laid out," Obama told reporters, even as France prepares to pull its troops out in 2012, a year earlier than planned.

Karzai said his country no longer wanted to be a "burden," urging the international community to complete a security transition to his Afghan forces as it pulls combat troops, currently numbering 130,000, by the end of 2014.

"Afghanistan... is looking forward to an end to this war and a transformational decade in which Afghanistan will be working further for institution building and the development of sound governance in the country," he said.

Along with reaffirming the 2014 deadline, the summit is expected to back Obama's plan to cede the lead in combat missions to Afghan troops next year, while making a commitment to securing $4 billion annually for Afghan forces.

A Western official told AFP Sunday that nations with troops in Afghanistan had pledged roughly $1 billion to bankroll Afghan security forces after 2014. The bulk of the funding is expected to come from the United States.

While NATO said the war effort was track, it faced more uncertainty over the reopening of key supply routes into Afghanistan, closed in November after botched US air strikes killed 24 Pakistani troops.

Pakistani President Asif Ali Zardari's attendance at the summit had raised hopes his government was ready to lift the 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 a sign of the waning appetite to engage in further conflict, NATO chief Anders Fogh Rasmussen said the western defense alliance was not prepared to intervene in Syria despite concern at the bloodshed there.

"We strongly condemn the behavior of the Syrian security forces and their crackdowns on the Syrian population and we urge the Syrian leadership to accommodate the legitimate aspirations of the Syrian people," he told reporters.

"But again NATO has no intention to intervene in Syria."

The summit in Obama's hometown went ahead under a massive security operation as normally bustling Chicago streets were deserted and monitored by police.

Boats with machine guns patrolled a river near Obama's hotel and the police and Secret Service enforced a wide security perimeter around the conference center. It was the first summit of the 28-member North Atlantic Treaty Organization on US soil in more than a decade.

Thousands of protestors have taken to the streets in recent days calling for an end to war. Although the rallies have been largely peaceful, scuffles broke out Sunday when some hardcore demonstrators refused police orders to disperse.

The NATO talks come against a backdrop of a changing geopolitical landscape for the 63-year-old organization which also has to confront shrinking defense budgets.

Leaders on Sunday launched the first phase of a US-led missile shield for Europe, risking the wrath of Russia which has threatened to deploy rockets to EU borders in response.

"We have decided to develop a NATO missile defense system, because we consider the missile threat a real threat, and against a real threat we need a real defense to protect our populations effectively," Rasmussen said.

But he added the dialogue with Russia would continue.

Obama and fellow leaders also agreed on a slew of some 20 joint projects to pool military hardware as part of a so-called "Smart Defense" initiative.