U.S. Chargé d’Affaires to the International Organizations in Vienna Howard Solomon made the previously unpublished comments, which were obtained by The Associated Press, at the Preparatory Commission of the Vienna-based Comprehensive Nuclear-Test-Ban Treaty Organization on Nov. 10.

“As President Trump indicated, the United States will begin testing activities on an equal basis with other nuclear-armed states. This process will begin immediately and proceed in a manner fully consistent with our commitment to transparency and national security,” Solomon said.

Solomon provided further explanation by noting, “For any who question this decision, context is important. Since 2019, including in this forum, the United States has raised concerns that Russia and China have not adhered to the zero-yield nuclear test moratorium,” he said, adding that the concerns “remain valid.”

Solomon’s comment referred to so-called supercritical nuclear test explosions banned under the Comprehensive Nuclear-Test-Ban Treaty, known as CTBT, where fissile material is compressed to start a self-sustaining nuclear chain reaction that creates an explosion.

The explosive tests produce an amount of energy released, referred to as nuclear yield, which defines a weapon’s destructive power. The treaty bans any nuclear explosion with a yield, even a very small one, following a zero-yield standard.

“Our concerns with Russia and China are in addition to the activities of North Korea, which has conducted six nuclear explosive tests this century,” Solomon said.

The global monitoring network established alongside the treaty in 1996 to register nuclear tests worldwide has detected all of North Korea’s six nuclear tests this century. Those were tests with larger yields.

However, the monitoring network is unable to detect very low-yield supercritical nuclear tests conducted underground in metal chambers, experts say.

The U.S. State Department did not immediately reply to a request for comment on whether Solomon was referring to low-yield supercritical nuclear tests.

China and Russia, which have signed but not ratified the treaty, say they adhere to a nuclear testing moratorium.

But since 2019, the U.S. State Department has publicly expressed concerns about China and Russia not adhering to their zero-yield testing moratoria. Annual reports on compliance with arms control agreements to the U.S. Congress cite possible activities at the Lop Nur nuclear testing site in the Xinjiang region of northwestern China and Russia’s Novaya Zemlya site, a remote Arctic archipelago.

In an interview for “60 Minutes” that aired Nov. 2 on CBS News, Trump said, “Russia’s testing, and China’s testing, but they don’t talk about it. You know, we’re an open society. We’re different. We talk about it.”

“They don’t go and tell you about it,” Trump continued. “You know, as powerful as they are, this is a big world. You don’t necessarily know where they’re testing. They — they test way under — underground where people don’t know exactly what’s happening with the test.”

In an interview for “60 Minutes” that aired Nov. 2 on CBS News, Trump said, “Russia’s testing, and China’s testing, but they don’t talk about it. You know, we’re an open society. We’re different. We talk about it.”

A White House official, asked for comment on whether Trump was referring to low-yield supercritical nuclear tests conducted underground, said the president had directed tests be done “on an equal basis” to other countries. The official spoke on condition of anonymity because they were not authorized to speak on the record about the testing plans.

Other countries have accelerated their testing programs, and Trump wants to act accordingly, the official said without providing further details.

Solomon’s comments in Vienna came in response to Russia’s Permanent Representative to the International Organizations, Mikhail Ulyanov, at a closed-door meeting of the Preparatory Commission of the CTBTO, an international body based in Vienna that monitors compliance with the nuclear test ban.

“The resumption of nuclear testing could cause significant damage to the nuclear non-proliferation regime and international security,” Ulyanov said.

“We consider it fundamentally important that the U.S. side provide a clear and detailed explanation of its position on the resumption of nuclear testing,” he added. “We expect the U.S. to respond appropriately and without further delay.”

Ulyanov also rejected the “completely unacceptable and unsubstantiated allegations” that Russia is conducting nuclear tests.

“These are false accusations. We consider such escalatory rhetoric unacceptable,” he said.