US President Donald Trump’s call to “immediately” resume testing of nuclear weapons, citing Beijing and Moscow’s rapid nuclear build-up, could drive China to “accelerate” its own efforts to develop its strategic forces, according to analysts.

On Thursday, Trump posted on social media that he had instructed the Pentagon to start testing USnuclear weapons “on an equal basis” with Russia and China because of “other countries’ testing programmes”.

“That process will begin immediately,” Trump said in a post published just a few minutes before hismeeting with Chinese President Xi Jinping in Busan, South Korea, on the sidelines of the Asia-Pacific Economic Cooperation (Apec) summit.

Trump said that while the US had more nuclear weapons than any other country – followed by Russia in second place and China as a “distant” third – Moscow and Beijing’s nuclear forces would catch up with Washington within five years.

In response to Trump’s order, the United Nations issued a rare direct rebuke.

“We shouldn’t forget the disastrous legacy of over 2,000 nuclear-weapons tests that have been carried out over the last 80 years,” UN spokesman Farhan Haq told reporters on Thursday. He said the UN and Secretary General Antonio Guterres believed “nuclear testing can never be permitted under any circumstances”.