NATO countries are expected to sign off Monday on U.S. President Barack Obama's exit strategy from Afghanistan that calls for an end to combat operations next year and the withdrawal of troops by the end of 2014.

Against a backdrop of massive demonstrations that saw violent clashes between protesters and police, NATO and world leaders gathered at the summit in Chicago to sketch out the end of an unpopular war and figure out how to pay for shoring up Afghanistan's security forces.

Obama made clear Sunday as the summit opened that he expects the NATO nations and their strategic partners to agree to the withdrawal plan, while assuring Afghan President Hamid Karzai that the 28-nation alliance would not abandon the country.

"Just as we have sacrificed together for our common security, we will stand together united in our determination to complete this mission," Obama said at the start of the summit.

Obama and Karzai, who met a day ahead of Monday's planned NATO talks on Afghanistan, both agreed that the end of the war was close at head.