NATO leaders agreed on Friday to develop a missile defense shield to protect the territory of all NATO states in Europe as well as the United States, U.S. President Barack Obama said.
The missile system will involve stationing U.S. interceptor missiles and radar in Europe. Officials have said the 28 NATO states will invest 200 million euros ($280 million) to link existing anti-missile systems to the U.S. system.
"It offers a role for all of our allies. It responds to the threats of our times," Obama told reporters at a NATO summit in Lisbon.
The leaders will invite Russia to join the system when they meet Russian President Dmitry Medvedev on Saturday.
"Tomorrow we look forward to working with Russia to build our cooperation with them in this area as well, recognizing that we share many of the same threats," Obama said.
The NATO military alliance began the summit in Lisbon earlier with an address to the assembled leaders by the organization's secretary general, Anders Fogh Rasmussen.
Rasmussen invited the leaders to join him in a moment of silence for the more than 2,200 NATO and allied soldiers who have died in the nine-year-old conflict in Afghanistan
"This summit is an important opportunity for us to align on approach and vision in Afghanistan," Obama told reporters, in brief remarks, at a joint appearance with the summit's host Portuguese President Anibal Cavaco Silva, while leaders gathered.
"I look forward to working with our NATO and our ISAF partners as we move towards a new phase, transition to Afghan responsibility which begins in 2011, with Afghan forces taking the lead of security across Afghanistan by 2014," he said.
U.S. leaders earlier said that NATO was ready to begin turning security over to Afghan forces next year, as the first step in a plan to withdraw almost all foreign troops from Afghanistan by the end of 2014.
Some senior NATO and Pentagon officials have expressed doubt that the 2014 deadline can be achieved, with the threat posed by Taliban insurgents to Afghanistan's weak government rising.
U.S. Secretary of State Hillary Clinton said in Lisbon before a NATO summit that the United States and the military alliance had listened to Afghan President Hamid Karzai, who has called for the 2014 deadline and were addressing his concerns.
Karzai will attend the summit and have talks with U.S. President Barack Obama at the summit on Saturday.
NATO leaders will formally announce the exit strategy at the summit, hoping to draw a line under a war widely seen as going badly for the United States and its allies. More than 2,200 foreign troops have been killed in the decade-long conflict.
"We will agree tomorrow on the beginning of a transition to Afghan security starting next year with the intention and goal of turning over Afghan security to the government and people of Afghanistan in 2014," Clinton said after talks with Portugal's foreign minister.
"At the same time there will be continued commitment of civilian support," she told reporters.
Other NATO states which face rising casualties are also calling for a withdrawal of combat troops by the end of 2014.
"We certainly don't want to be in a combat role ... but even then after 2014, when the Afghan government takes control, they are going to require help and advice," British Defense Secretary Liam Fox told BBC radio.
NATO leaders will also approve a new 10-year vision for NATO, underscoring the need for the 28-nation alliance to be ready for similar missions in the future, despite Afghanistan's setbacks.
In an opinion piece and an interview before the summit, Obama said the U.S. troop reductions would begin next July and reaffirmed commitment towards a reconciliation with the Taliban, who are fighting the Afghan government and foreign troops.
"America and our NATO allies strongly support a ... process that seeks reintegration into society of those Taliban who agree on some main points: they have to abandon violence, break their ties with al-Qaeda and agree to live under the rules of the Afghan Constitution," Obama told Spain's El Pais newspaper.
"This reconciliation begins with a dialogue with the insurgent forces and must be led by the Afghans themselves," he said.
The U.S.-led intervention in Afghanistan began in response to the Sept. 11, 2001, attacks after the then-ruling Taliban refused to hand over al-Qaeda leader Osama bin Laden.
Now in its 10th year, the war has become a political headache for Obama. Foreign casualties have hit record levels.
The withdrawal strategy hinges on efforts to build up Afghan forces so they can contain the widening insurgency, with a target strength set at more than 300,000 by the end of 2011.
The leaders were also expected to agree to extend a missile defense system and underline the importance of cooperation with strategic partners such as Russia, through which NATO wants help to broaden its supply routes to Afghanistan.