China pushes largest-ever expansion of nuclear arsenal

The SIPRI think tank estimates that China has a stockpile of around 350 nuclear warheads -- small fry when compared with the United States and Russia.

But it is growing fast, and could have 1,500 warheads by 2035, according to a Pentagon estimate published in November.

"China appears to no longer be satisfied with just a few hundred nuclear weapons to ensure its security," Matt Korda, of the Federation of American Scientists, said .

Since its first nuclear test in 1964, China has been content to maintain a comparatively modest arsenal and has maintained that it will never be the first to use nuclear weapons in a conflict.

But in recent years, under President Xi Jinping, it has begun a massive military modernisation drive that includes upgrading its nuclear weapons to not only deter foes but also be able to counter-attack if deterrence fails.

"China is undertaking the most significant expansion and modernization of its nuclear forces in the country's history," David Logan, an assistant professor at the US Naval War College, said .

This involves not only ramping up the production of warheads, but also upgrading the ability to deliver them with a nuclear triad: missiles, aircraft and submarines.

"The changes that are taking place or under way are very significant" and "will turn China from a state that has a nuclear retaliatory capability to one that is the world's third major nuclear power", Eric Heginbotham, Principal Research Scientist at MIT's Center for International Studies, said .

"This will mark the first time in history that the big nuclear powers will need to consider not one potential nuclear competitor, but two, and it will have implications for nuclear planning and stability everywhere."

China is "rapidly" building launch facilities for intercontinental ballistic missiles, with more than 300 silos in total, according to the Pentagon last year.