China Tuesday said it will continue to "modernise" its nuclear arsenal and called on the United States and Russia to reduce their stockpiles a day after global powers pledged to prevent such weapons spreading.

In a rare joint statement setting aside rising West-East tensions, the United States, China, Russia, Britain and France reaffirmed their goal of creating a world free of atomic weapons and avoiding a nuclear conflict.

The five nuclear powers also committed to full future disarmament from atomic weapons, which have only been used in conflict in the US bombings of Japan at the end of World War II.

But squaring that rhetoric with reality will not be easy at a time of heightened tension between those same global powers.

There are growing global concerns about China's military modernisation especially after its armed forces last year announced they had developed a hypersonic missile that can fly at five times the spread of sound.

The United States has also said China is expanding its nuclear arsenal with as many as 700 warheads by 2027 and possibly 1,000 by 2030.

On Tuesday, China defended its nuclear weapons policy and said Russia and the United States -- by far the world's largest nuclear powers -- should make the first move on disarmament. 

"The US and Russia still possess 90 percent of the nuclear war heads on Earth," Fu Cong, director general of the department of arms control at the Chinese foreign ministry, told reporters. 

"They must reduce their nuclear arsenal in an irreversible and legally binding manner."

Fu hit back at Washington's allegations. 

"On assertions made by US that China is vastly increasing its nuclear capabilities, this is untrue," Fu said.

"China has always adopted the no first use policy and we maintain our nuclear capabilities at the minimal level required for ou national security."

"China will continue to modernise its nuclear arsenal for reliability and safety issues," he added. 

Ties between Beijing and Washington have been strained over a series of issues including China's intentions to reunite independently-governed Taiwan -- by force if necessary.

Fu dismissed speculation over the possibility of deploying nuclear weapons near the Taiwan Strait.

"Nuclear weapons are the ultimate deterrent, they are not for war or fighting," he said.