War between the world's two major powers is no longer "inconceivable".

That's one of the messages Ambassador-at-Large Tommy Koh offered in an op-ed published in The Straits Times on Tuesday, June 2.

His piece is an ode to the U.S. for being a world leader and constant democratic work-in-progress.

America wants to defend its supreme position

Koh's piece, "A birthday letter to America", came two days before America's Independence Day on July 4.

Writing on his biggest worry about the future of the U.S., Koh said war between the U.S. and China is no longer something that exists in the realm of fantasies -- although both countries need not go to war ultimately.

The precipitating factor?

For the first time since the end of the Cold War, the Americans are faced with the possibility of being overtaken by China, a secondary power.

And the U.S. is not necessarily used to being relegated to being No. 2 in the global system, Koh opined.

Moreover, the Americans think the Chinese harbour the aspirations of displacing the U.S. from its current No. 1 position, which is a perception that might not be true, Koh added.

To retain the top spot, the U.S. is willing to take on any challenger to its long-held supremacy, he said.

Overreach by China, overreaction by America

Koh then raised a point by former U.S. deputy assistant secretary of state Susan Shirk, who described current tensions between the two countries as "overreach by China and overreaction by America".

China's overreach is exemplified by its behaviour in the South China Sea.

It is seen as being overly assertive when it comes to its excessive territorial claims, land reclamation works, and construction of military facilities on the disputed islands.

China also plans to dominate the hi-tech industry -- it declared its "Made in 2025" strategy in 2015.

As for overreaction by the U.S., Shirk warned of the dangers of the prevailing perception that China presents a threat, which might end up damaging American interests.

And decoupling the two economies would be disastrous, she said.

U.S. & China can cooperate & compete

Koh said there is nothing against both countries working together even while competing against each other.

This is possible should they play by the same rules and recognise that they share much more in common than differences.

Finally, he said many in Asia want the U.S. to be a strong and self-confident country, and to "continue to lead the world with wisdom and generosity".

State leaders in the region, such as Malaysia's Prime Minister Mahathir Mohamad, recently cautioned against going to war in response to the U.S.-China trade dispute.

He admonished countries to strive for peace instead:

Top image by Sulaiman Daud