WASHINGTON, United States (AFP) — 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.

“Russia’s testing, and China’s testing, but they don’t talk about it,” he told CBS’ “60 Minutes” program, in an interview released Sunday.

“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.

China denied testing nuclear weapons on Monday.

“China has always adhered to the path of peaceful development, pursued a policy of no first use of nuclear weapons, upheld a self-defense nuclear strategy and abided by its commitment to suspend nuclear testing,” foreign ministry spokesperson Mao Ning said.

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.

The announcement came in the wake of Russia saying it had tested a new nuclear-powered cruise missile, the Burevestnik, and a nuclear-powered and nuclear-capable underwater drone.

Asked directly if he planned for the US to detonate a nuclear weapon for the first time in more than three decades, Trump told CBS: “I’m saying that we’re going to test nuclear weapons like other countries do, yes.”

No country other than North Korea is known to have conducted a nuclear detonation for decades.

Russia and China have not carried out such tests since 1990 and 1996 respectively.

Pressed on the topic, Trump said: “They don’t go and tell you about it.”

“As powerful as they are, this is a big world. You don’t necessarily know where they’re testing.”

“They test way underground where people don’t know exactly what’s happening with the test. You feel a little bit of a vibration,” he added.