“In Lisbon, we agreed to create a NATO missile defense system. Today, in Chicago, we have declared that a reality,” Rasmussen told reporters on Sunday. “We call this an Interim Capability.”

Following the Lisbon decision, NATO started developing a command and control system capable of connecting missile defense assets provided by individual Allies into a coherent defense, NATO said on its website.

“It is the first step towards our long-term goal of providing full coverage and protection for all NATO European populations, territory and forces. Our system will link together missile defense assets from different Allies - satellites, ships, radars and interceptors - under NATO command and control,” Rasmussen said on Sunday.

“It will allow us to defend against threats from outside the Euro-Atlantic area,” he said.

NATO said on its website: "The Interim Capability features a basic command and control capability which has been tested and installed at Headquarters Alliance Air Command in Ramstein, Germany. Allies will provide sensors and interceptors to connect to the system."

The Full Operational Capability is expected around 2020 or early next decade, it said.

Russia and NATO agreed to cooperate on the so-called European missile defense system at the Lisbon summit in November 2010. NATO insists there should be two independent systems that exchange information, while Russia favors a joint system with full-scale interoperability.

Chief of Russia’s General Staff, Army General Nikolai Makarov said in early May that Russia does not exclude preemptive use of weapons against NATO’s missile defense systems in Europe but only as a last resort.

The projected European missile defense system could by 2020 have the ability to intercept Russian intercontinental ballistic missiles, Secretary of Russia’s Security Council Nikolai Patrushev said earlier.

The United States and NATO agreed to develop the system at a summit in Lisbon in 2010, but talks between Russia and the alliance have floundered over NATO’s refusal to grant Russia legal guarantees that the system would not be aimed against Russia’s strategic nuclear deterrent.

NATO and the United States insist that the shield would defend NATO members against missiles from North Korea and Iran and would not be directed at Russia.