keeping NATO strong and capable in the 21st century and keeping our global network of partners solid," Rasmussen told reporters.
Despite plans by France to speed up its own pullout, he pledged: "There will be no rush for the exits. We will stay committed to our operation in Afghanistan and see it through to a successful end."
World leaders and international organizations were due to open their two-day summit later Sunday aimed at cementing a 2014 withdrawal deadline from the decade-long war in Afghanistan and handing over security to Afghan forces.
They were meeting amid tight security in US President Barack Obama's hometown of Chicago, with police deployed along the main arteries, some on horseback, as Coast Guard boats mounted with machine guns patrolled the river.
It is the first summit of the 28-member North Atlantic Treaty Organization on US soil in more than a decade, and comes as the 63-year-old organization confronts shifting 21st-century realities and shrinking defense budgets.
Apart from Afghanistan, Obama and his fellow leaders will take other key decisions, activating the first part of a missile shield for Europe, despite fierce Russian opposition and announcing a slew of military cooperation projects to cope with mounting austerity.
Among the world leaders at the table with Obama will be Afghan President Hamid Karzai and his Pakistani counterpart Asif Ali Zardari, who accepted a last-minute invitation to attend.
Despite the stubborn Taliban insurgency, war-weary international forces are seeking to hand control of security to Afghan forces while withdrawing some 130,000 foreign combat troops by the end of 2014.
"This (summit) will be a powerful demonstration of the commitment of the whole international community to the future of Afghanistan," Rasmussen told reporters.
But France has shaken up the carefully crafted withdrawal plan with new President Francois Hollande saying that he plans to pullout French troops by late 2012, a year earlier than planned.
German Chancellor Angela Merkel said Sunday: "Germany supports NATO's idea: We went into Afghanistan together and we want to withdraw from Afghanistan together."
She dismissed any notion that an early French departure would place an extra burden on the German contingent in Afghanistan.
"I think France will make it clear at the summit what form its commitment will take. I think we still need to wait a little bit longer. We would hope that France would stay within ISAF," she added.
Karzai comes armed with a firm demand for $4.1 billion (3.2 billion euros) a year to fund his security forces after the pullout.
The United States is expected to foot half the bill while hoping the international community will stump up the rest.
Washington is also hoping that Zardari will agree to reopen key NATO supply routes into Afghanistan closed in November after US air strikes killed 26 Pakistani troops.
But the US-Pakistani talks on reopening vital supply routes for NATO forces in Afghanistan have stumbled over Islamabad demand to charge steep fees for trucks crossing the border, a senior US official told AFP.
The official confirmed that Pakistan has proposed an exponential increase in fees, from the current rate of about $250 per truck to "thousands of dollars."
"That's, in a word, unacceptable," he said.
Governments are feeling the pinch as Europe's debt crisis forces budget cuts across the board, and to cope NATO will announce more than 20 joint projects to pool military hardware as part of a so-called "Smart Defense" initiative.
NATO has touted a planned US-led missile shield for Europe as a shining example of military cooperation.
A first step to the shield will be the announcement at the summit of an "interim capability" putting a US warship armed with missile interceptors in the Mediterranean, and a radar system based in Turkey under NATO command.