(Epoch Times) President Donald Trump on Wednesday ordered the Pentagon to begin conducting nuclear weapons tests again after a three-decade moratorium on the practice.

“Because of other countries’ testing programs, I have instructed the Department of War to start testing our Nuclear Weapons on an equal basis,” Trump wrote in a post on Truth Social. “That process will begin immediately.”

Trump posted the statement just before he was set to meet with Chinese leader Xi Jinping in South Korea, where the two discussed trade issues.

Nuclear tests in the atmosphere, space, or underwater have been banned since the 1963 Limited Test Ban Treaty, which permitted continued underground nuclear testing for several decades.

The United States last conducted a nuclear weapons test underground in September 1992.

That year, President George H.W. Bush announced that the United States would undertake a unilateral moratorium on all nuclear weapons testing, including those conducted underground.

Similarly, China conducted its final nuclear weapons test underground in 1996, after which it declared a moratorium on nuclear testing the nation has since followed.

Trump tied the decision to resume nuclear testing to his first administration’s efforts to keep the United States’ nuclear arsenal on par with those of Russia and China.

“The United States has more Nuclear Weapons than any other country. This was accomplished, including a complete update and renovation of existing weapons, during my First Term in office. Because of the tremendous destructive power, I HATED to do it, but had no choice! Russia is second, and China is a distant third, but will be even within 5 years,” Trump wrote.

It’s unclear from his Truth Social post whether the resumed tests would be conducted underground, underwater, in the atmosphere, or in space, though underground testing has been preferred by nuclear-armed powers since the potential risks of in-atmosphere or underwater tests for the environment have become clearer.

This is the most likely route for any U.S. nuclear tests conducted in the future, as the United States has abided by the Limited Test Ban Treaty of 1963 for over 60 years.

Then, just hours ahead of Trump’s visit to South Korea, North Korea announced that it had tested a nuclear-capable cruise missile in the sea to its west.

However, it’s been years since the last nuclear weapon detonation was conducted. The last confirmed nuclear test resulting in a detonation was carried out in September 2017 by North Korea. It was conducted underground and detected by U.S. seismic technology.

It’s unclear whether Trump will seek to resume full-scale detonations of nuclear devices, or if the Pentagon will instead test nuclear delivery technology, similar to the recent tests conducted by Russia and North Korea.

Rather than through real-life detonations, nuclear weapons have been “tested” through refined computer simulations, researching subcritical nuclear reactions in controlled settings, and similar methods not relying on nuclear detonation.