The agreement, according to the president, followed a year of talks to determine the best ways to coordinate efforts to protect members of the 61-year-old alliance. 

The system would be "strong enough to cover all NATO European territory and populations, as well as the US", Obama told reporters in Lisbon, Portugal. 

The missile defense plan "offers a role for all of our allies in response to the threats of our times. It shows our determination to protect our citizens from the threat of ballistic missiles", the he said.  

NATO Secretary-General Anders Fogh Rasmussen announced on November 19 that heads of state had agreed to a new mission statement, calling it the alliance's "road map for the next 10 years". Crafting this so-called strategic concept had been a top priority of the meeting, which Rasmussen last month deemed "one of the most important summits in the history of our alliance".