Leaders of the 28-nation alliance gathered in Chicago are expected to endorse plans for the NATO-led International Security Assistance Force to hand over command of all combat missions to Afghan forces by the middle of 2013 and for the withdrawal of most of the 130,000 foreign troops by the end of 2014.
NATO has also been seeking to secure long-term support for the Afghan police and army, whose ability to battle the Taliban is vital for the alliance's aim of a smooth exit and future Afghan stability.
While he said the summit was "not a pledging conference", NATO Secretary-General Anders Fogh Rasmussen was "optimistic about reaching the overall goal."
French President François Hollande vowed at the summit to stick to his election pledge to withdraw French troops by the year's end – two years earlier than the NATO timetable.
The alliance is also set to announce that its new ballistic missile defence system has reached what it calls "interim operational capability".
But NATO's missile defence plans are not without their critics. Moscow has signalled its opposition to the scheme, with Russian generals even going so far as to threaten to deploy nuclear-capable Iskander missiles against the NATO missile defence sites in Romania and Poland.
Russia is represented at the NATO summit by the country's special envoy to Afghanistan, Zamir Kabulov.
Enlargement off the table
In contrast with previous summits, this time NATO enlargement has been largely kept off the table.
Bosnia, Georgia, Macedonia and Montenegro aspire to become NATO members. But alliance experts say the Chicago summit will not deal with enlargement and will not invite new countries to become members.
According to a transcript of a government session in Athens, published by the website of the Greek president, political leaders openly spoke of resorting to a veto to block the accession of the Former Yugoslav Republic of Macedonia, as Macedonia is known internationally, until the “name issue” is solved (see background).
Greece blocked Macedonia's entry into NATO at a 2008 summit in Bucharest.
Regarding Georgia, the country’s NATO accession has been on the back burner since the brief August 2008 war with Russia over the breakaway regions of Abkhazia and South Ossetia. Moscow has since recognised both as independent nations, further fuelling tensions with Georgia.
But Georgian President Mikheil Saakashvili said he was happy that his country was now listed together with the three Western Balkan countries as a NATO aspirant.
"What we are getting now [is] Georgia listed together with three Balkan countries and frankly everybody knows that they will join NATO. So from that point of view it is progress and it demonstrates movement forward," Saakashvili said in Chicago, quoted by the website Civil Georgia.
Saakashvili also said putting Georgia into the "basket of Balkan countries" had a geographical dimension, amounting to putting his country into the West thanks to those reforms which it had implemented.
Heavy security has been put in place for the Chicago summit and police clashed with anti-war protestors marching by the thousands near the venue.
Three NATO summit activists arrested on terrorism charges were plotting an attack on President Barack Obama's campaign headquarters in Chicago, prosecutors said Saturday.