China said on Tuesday it will continue to "modernise" its nuclear arsenal and called on the United States and Russia to reduce their own stockpiles a day after global powers pledged to prevent such weapons from 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 spiralling tensions between those same global powers not seen since the Cold War.

There are growing global concerns about China's rapid 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 warheads 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 dismissed US claims that China was vastly increasing its nuclear capabilities.

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

But he said Beijing would "continue to modernise its nuclear arsenal for reliability and safety issues".

Beijing said it would continue to 'modernise' its nuclear arsenal, a day after joining the four other major nuclear powers in pledging to prevent such weapons spreading
Beijing said it would continue to 'modernise' its nuclear arsenal, a day after joining the four other major nuclear powers in pledging to prevent such weapons spreading AFP / GREG BAKER

Ties between Beijing and Washington have been strained over a series of issues including China's intentions to take Taiwan, which it claims as part of its territory, by force if necessary.

Beijing's sabre-rattling towards Taiwan has reached new heights under President Xi Jinping, China's most authoritarian leader in a generation.

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.

While the United States and Russia have had a formal strategic stability dialogue since the days of the Cold War, producing several disarmament agreements, that is not the case between Washington and Beijing.

In Europe, tensions with Moscow have deteriorated over a Russian troop build-up close to the Ukrainian border.

That has raised fears that the Kremlin, worried by the possibility of further eastward expansion of NATO, is planning a new attack on its pro-Western neighbour.

Crunch talks between Russia and the US on European security are expected in Geneva on January 10.

Against this backdrop, Monday's joint statement on nuclear weapons was a rare moment of consensus between the UN's five permanent Security Council members.

"A nuclear war cannot be won and must never be fought," the statement said, adding that "further spread of such weapons must be prevented".

The statement was issued after the latest review of the Treaty on the Non-Proliferation of Nuclear Weapons (NPT) -- which first came into force in 1970 -- was postponed from its scheduled date of January 4 to later in the year due to the Covid-19 pandemic.

The statement also pledged to abide by a key article in the NPT under which states committed to full future disarmament from nuclear weapons.

The joint statement also came as the world powers seek to reach an agreement with Iran on reviving the 2015 deal over its controversial nuclear drive, which was rendered moribund by the US walking out of the accord in 2018.