Trump says Russia, China have secretly tested nuclear weapons

PRESIDENT Donald Trump alleged Sunday that countries including Russia and China have conducted underground nuclear tests unknown to the public, and that the US would follow suit.

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"Russia's testing, and China's testing, but they don't talk about it," he told CBS's "60 Minutes" programme, in an interview released at the weekend.

"I don't want to be the only country that doesn't test," he said, adding North Korea and Pakistan to the list of nations allegedly testing their arsenals.

Confusion has surrounded Trump's order that the US begin testing, particularly if he meant conducting the country's first nuclear explosion since 1992.

The 79-year-old Republican first made his surprise announcement by social media post on Thursday, minutes before entering a summit with Chinese leader Xi Jinping in South Korea.