China President Xi Jinping stated that China would always uphold world peace and international rules, despite worries expressed by the US and other countries about China's rising global assertiveness.

The remarks came after Taiwan said that military tensions with China were at their worst in over 40 years, amid rising fears that the neighbour will try to retake the self-ruled island it claims as its own by military force.

Xi said in a speech marking the 50th anniversary of China's return to the UN that it would always be a "builder of world peace" and an "international order protector".

The UN decided in 1971 to recognise the People's Republic of China as China's sole representative, removing Taiwan from the world body.

China has also more assertively staked its claims to disputed territory on its Himalayan border with India, tracts of the South China Sea disputed with some Southeast Asian nations and some East China Sea islands disputed with Japan.

"China vehemently opposes all forms of hegemony and power politics, unilateralism and protectionism," said Xi, urging increased global cooperation on problems such as regional conflicts, terrorism, climate change, cybersecurity, and biosecurity.

Xi called for all countries to support the values of peace, development, justice, democracy, and freedom, using the phrase "shared values of all mankind," which he coined and first used in a July speech commemorating the ruling Chinese Communist Party's 100th anniversary.

Xi stated that global governance reforms are required, and that international rules should be decided by all 193 UN members, rather than "particular nations or country groupings," implying a veiled criticism of the US' dominant influence over international institutions.

He also stated that all countries should always follow international rules, not just when the rules suit them.