However, as common threats disappeared after the Cold War, rifts among NATO countries began to rise. In 2003, NATO member states, led by Germany and France, publicly condemned the U.S. military strike against Iraq, triggering a deep internal split among NATO members.

In addition, NATO members are deeply divided on what the alliance should be in the future. The Central European and Baltic members want the bloc to reaffirm the Article V to counter possible threats from Russia.

German and France no longer regard Russia as a military threat and want cooperation with Russia on European security. They also insist on putting stricter limits on NATO's mission beyond its borders.

The U.S. and Britain regard the security situation in Europe largely in benign terms and think NATO should operate outside Europe in the future while improving its capabilities for tackling new emerging threats.

In the new concept, the alliances need badly to find ways to serve member's interests. NATO officials say the the concept will reaffirm the alliance's policy of collective defense and Article V will address non-traditional threats from missiles, cyber attacks and nuclear proliferation.

It is believed that threats against NATO members cannot be properly tackled by NATO only now. In the coming years, the alliance needs to develop ties with the EU, Russia, other regional powers, the U.N. and other international organizations.

NATO Secretary General Anders Fogh Rasmussen said that the definition of territorial defense in today's world has changed and NATO has to go beyond its borders to fulfill its core mission.

"NATO has no ambition to become the world's policeman but if we are to make territorial defense effective, we need a global perspective in our policies," he said.

Analysts believe that as the international security environment changes dramatically, NATO's role as a regional military alliance will eventually peter out.

"Compared to its first decade, NATO between 2010 and 2020 is likely to appear less often on the central stage of global affairs," according to a May report from the so-called Group of Experts.

"Instead, it will be cast in a variety of roles, sometimes as a leader, at other times in a supporting capacity sharing the spotlight with partners and friends," the report said.