In Afghanistan, it is battling Al Qaeda and Taliban. in newly independent Kosovo, it’s up against Serbian protesters armed with firebombs and grenades. And behind the scenes, it is helping to quell the violence in Iraq and to track down suspected war criminals in Bosnia.

NATO, its chief insists, has no ambitions to become a “global policeman.” But the military alliance born of the Cold War continues to grow and face new challenges.

At a summit Wednesday through Friday in Romania, President Bush and the leaders of NATO’s other 25 countries will discuss how to mobilize more troops to turn the tide in Afghanistan, and whether to get bigger and tougher at the risk of alienating Russia.

The North Atlantic Treaty Organization, which turns 60 next year, faces a mid-life crisis as it debates whether a new vision and direction are needed in a world transformed since the Cold War that was the alliance’s original raison d’être.

Its membership has nearly doubled since the Berlin Wall came down, and the venue of the summit — the cavernous “People’s House” in Bucharest, built by Romania’s last communist dictator, Nicolae Ceausescu — is a powerful symbol of a world upended.

Yet echoes of the Cold War persist in NATO’s confrontation with Russia.