A missile defence system covering all Nato countries has been agreed at the alliance's summit in Lisbon, US President Barack Obama has said.
The shield would cover all Nato members in Europe and North America.
Nato is also backing the swift ratification of the Start treaty between the US and Russia, cutting nuclear weapon stockpiles.
The summit will discuss Afghanistan on Saturday, with plans to end combat operations by 2014.
Nato will ask Russia to co-operate on missile defence and join the system.
On Saturday, leaders will meet Russian President Dmitry Medvedev, who is attending the summit.
Missile defence has been a point of tension between Nato and Russia in the past, but President Medvedev's presence at the summit is being seen as a strengthening of ties.
BBC News
