NATO will be 70 on April 4. It is a timely occasion for the world's largest military alliance to reflect on whether it has helped make the world a safer place, and whether it has a role to play today.

Born in the Cold War era and bearing the brunt of military confrontation between the United States and the former Soviet Union, NATO expanded eastward to take in more members after the Soviet Union's collapse and it now comprises 29 North American and European countries.

Yet rather than upholding its intended purpose of mutual defense in response to an attack by an external party, the world has been witness to its aggression as other NATO members have supported the United States in the many wars and military operations it has launched against a string of sovereign states under various excuses.

Ironically, despite allowing the US to lead it by the nose, it is the US that has become NATO's biggest existential threat. Since entering the White House, each time US President Donald Trump has attended a NATO meeting, he has blown it up, questioning NATO's value to the US, and whether it should continue its commitment to its allies.

On Tuesday, two days before NATO marks its 70th anniversary, Trump again urged his European allies to increase military expenditure, claiming that the US is paying a "very big" and "disproportionate share" for defending Europe.

This attitude has become the most pressing challenge to the alliance.

Yet from the first Gulf War to Afghanistan, NATO members have participated in all the US waged wars, and its military intervention footprints now extend from the Middle East to Europe, Asia, Africa and Latin America.

Each time, the US and NATO have produced justifications for these military operations — claiming they are for humanitarian or anti-terrorism purposes. And each time, the world has found it increasingly difficult to buy their excuses. So too have some NATO members.

Intrinsically, the problems NATO faces stem from the confusion among its members over what role the alliance should play amid the changing international reality.

In recent years, there has been a rising trend for international community to seek to resolve issues through dialogue and consultations, rather than force. And whether it is responding to the menace of nontraditional security threats or trying to project its power, NATO has to learn to coexist with others in a harmonious way and try to work with them to address global challenges.

To strengthen its raison d'être and credibility in a world that has fundamentally changed from that in which it was born, NATO should seek to play a constructive role in defending world peace and stability.