CHICAGO - Meeting with NATO leaders to determine the "next milestone" toward ending the war in Afghanistan, President Obama today vowed that Afghans "will not stand alone" as they take over security responsibility from NATO forces.

"Our nations and the world have a vital interest in the success of this mission," the president told leaders of NATO nations that have participated in the war. "I am confident, because of the leadership represented here as well as the leadership of our outstanding armed forces, that we can advance that goal today and responsibly bring this war to an end."

The leaders are meeting today to solidify "the next phase of the transition" as Afghan security forces ready to assume the lead next year. NATO will adopt a supporting role before ultimately withdrawing at the end of 2014.

The United States is also urging its NATO allies, many of which are cash-strapped, to pitch in financially. It will cost roughly $4 billion a year to support Afghan security forces after NATO withdraws.

"Over the past two years, we've made important progress," the president said. "Our forces broke the Taliban's momentum. More Afghans are reclaiming their communities. Afghan security forces have grown stronger. Today is also an opportunity to ensure our hard-won progress is preserved.

"Today, we can agree on NATO's long-term relationship with Afghanistan beyond 2014, including our support of Afghan security forces," Obama said. "As Afghans stand up, they will not stand alone."