China is on course to develop an arsenal of up to 1,000 nuclear weapons within six years, the head of Nato has warned.

Jens Stoltenberg, Nato’s secretary general, said the communist state was investing heavily in modern weaponry, including nuclear missiles, which would grow to 1,000 warheads by 2030.

He added that the dual threats of nuclear armed adversaries – China and Russia – was a new threat to the west and Nato which could no longer be ignored.

Mr Stoltenberg said: “And that means that in a not very distant future Nato may face something that it has never faced before, and that is two nuclear-powered potential adversaries – China and Russia. Of course, this has consequences.”

The ramifications of that Russia and China’s alliance meant that Nato was now in talks to deploy more nuclear weapons to counter the growing threat.

The head of the alliance revealed there were live consultations between members on taking missiles out of storage and placing them on standby as he called for transparency to be used as a deterrent.

Mr Stoltenberg said: “I won’t go into operational details about how many nuclear warheads should be operational and which should be stored, but we need to consult on these issues. That’s exactly what we’re doing.”

The Nato chief said nuclear transparency should be the cornerstone of Nato’s nuclear strategy to prepare the alliance for what he described as a more dangerous world, in an interview with the Daily Telegraph.

A decade ago when he assumed his role, nuclear exercises were conducted in complete secrecy.

Now he openly praises a number of its 32 allies for contributing to the deterrent, including most recently the Netherlands for investing in dual-capable fighter jets that can host US nuclear weapons.

He added: “Transparency helps to communicate the direct message that we, of course, are a nuclear alliance.

“Nato’s aim is, of course, a world without nuclear weapons, but as long as nuclear weapons exist, we will remain a nuclear alliance, because a world where Russia, China and North Korea have nuclear weapons, and Nato does not, is a more dangerous world.”

Mr Stoltenberg’s warnings come after the G7 sharply criticised China and Russia in a communique that called on Beijing to stop supplying weapons technology to Moscow and opposed China’s “militarisation” in the Pacific.

Both the US and UK have committed their nuclear deterrents to Nato, while other European allies share the burden of the responsibility by storing weapons on their territory and investing in the systems to launch them.

The number of operational nuclear weapons is top secret but estimates suggest the UK has about 40 of 225 deployed at any one time. The US has about 1,700 of 3,700.

France, Nato’s third nuclear power, does not make its atomic arsenal available to the alliance because of a long-held decision to maintain independence over its own deterrence.

Mr Stoltenberg insisted that the US and its European allies were now modernising their nuclear deterrent in the face of increased threat from Russia.

He said: “The US is modernising their gravity bombs for the nuclear warheads they have in Europe and European allies are modernising the planes which are going to be dedicated to Nato’s nuclear mission.

“Then, of course, you have the United Kingdom, which is special because the United Kingdom has its own nuclear weapons.”

Mr Stoltenberg’s comments follow claims by the International Atomic Energy Agency that Iran was expanding its uranium-enrichment capacity at two underground sites.

The disclosure led to  the US State Department warning Iran that its plans  for uranium enrichment had  no “credible peaceful purpose”.

The US statement said: “The report issued today by the IAEA makes clear that Iran aims to continue expanding its nuclear program in ways that have no credible peaceful purpose. These planned actions further undermine Iran’s claims to the contrary. If Iran implements these plans, we will respond accordingly.”

Dr Wilfred Wan, Director of Stockholm International Peace Research Institute, said: “We have not seen nuclear weapons playing such a prominent role in international relations since the end of the Cold War. It is hard to believe that barely two years have passed since the leaders of the five largest nuclear-armed states jointly reaffirmed that “a nuclear war cannot be won and must never be fought”.