China's defence minister on Thursday urged greater efforts for global unity, warning against an increasingly divided world "defined by the rule of the jungle".

Speaking to formally open the Beijing Xiangshan Forum on security, Dong Jun said the world was overshadowed by Cold War thinking, hegemony and protectionism.

"External military interference, seeking spheres of influence and coercing others to take sides will bring the international community into chaos," Dong said, adding that the world was at another "crossroads" and had to choose dialogue over confrontation.

Dong's remarks contained several veiled swipes at the United States and appeared more hawkish than his speech to open last year's forum.

"An obsession with absolute superiority in military strength and a 'might is right' approach will lead to a divided world defined by the rule of the jungle and disorder," Dong said.

A strong Chinese military would be a force for peace, he added.

Dong's remarks follow recent speeches by President Xi Jinping against "hegemonism and power politics" and a large military parade in Beijing earlier this month that unveiled a host of new weapons.

His remarks come amid simmering tensions between China and the U.S. and its allies and partners over flashpoints across East Asia, including Taiwan and the South China Sea, as well as broader economic rivalries under the administration of U.S. President Donald Trump.

While saying that China was open to doing its part to uphold the international order, Dong said the People's Liberation Army would never allow any Taiwan "separatist" attempts to succeed.

"The return of Taiwan to China is an integral part of the postwar international order," he said, adding that it was ready "to thwart external military interference at all times".

China claims Taiwan as its territory and has never renounced the use of force to seize it.

Taiwan's President Lai Ching-te and his government strongly object to China's sovereignty claims, saying it is up to the island's people to decide their own future.

Some 1,800 representatives from 100 countries, including officials, military personnel and scholars, are attending the annual three-day event, China's official Xinhua news agency reported.

Most Western nations have sent relatively low-level diplomatic representatives to the forum, with some saying they are seeking to learn more about China's ongoing military build-up and opaque military leadership.

The forum ends on Friday.