President Donald Trump, left, and Chinese President Xi Jinping pose together ahead of their summit talk at Gimhae International Airport in Busan, South Korea, Thursday. (AP Photo/Mark Schiefelbein)

BUSAN, South Korea (AP) — President Donald Trump appeared to suggest the U.S. will resume testing nuclear weapons for the first time in three decades, saying it would be on an “equal basis” with Russia and China.

The Kremlin pointed out that a global ban on nuclear tests has remained in place, but warned that if any country resumes nuclear testing, Russia would follow suit.

There was no indication the U.S. would start detonating warheads, but Trump offered few details about what seemed to be a significant shift in U.S. policy.

He made the announcement on social media minutes before he met with Chinese leader Xi Jinping on Thursday in South Korea to discuss trade. He offered little clarity when he spoke to reporters later aboard Air Force One as he flew back to Washington.

The U.S. military already regularly tests its missiles that are capable of delivering a nuclear warhead, but it has not detonated the weapons since 1992. The Comprehensive Nuclear Test Ban Treaty, which the U.S. signed but did not ratify, has been observed since its adoption by all countries possessing nuclear weapons, North Korea being the only exception.

Trump suggested, however, that changes were necessary because other countries were testing weapons. It was unclear what he was referring to, but it evoked Cold War-era escalations.

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

Asked about Trump’s comments, Kremlin spokesman Dmitry Peskov reaffirmed an earlier warning from Russian President Vladimir Putin, who said Moscow would resume nuclear tests if others do so first.

“If someone abandons the moratorium, Russia will act accordingly,” Peskov said in a call with reporters.

The White House did not immediately respond to questions seeking more details.

When Trump spoke to reporters later, he appeared to be conflating the testing of missiles that deliver a nuclear warhead with the testing of the warheads.

Other countries, he said, “seem to all be nuclear testing,” but when it comes to the U.S., “We have more nuclear weapons than anybody. We don’t do testing.”

“I see them testing and I say, well, if they’re going to test, I guess we have to test,” Trump said as he continued speaking to reporters.

Trump was asked where the tests would occur and he said, “It’ll be announced. We have test sites.”

Pentagon officials didn’t immediately respond to questions about the announcement from Trump on the nuclear missile tests.

Vice Admiral Richard Correll, Trump’s nominee to lead the military command in charge of the nation’s nuclear arsenal, was pressed by U.S. senators at his confirmation hearing Thursday to try to interpret the president’s comments.

“I wouldn’t presume that the president’s words meant nuclear testing,” Correll said.

“Well, that’s what he said,” Sen. Mazie Hirono, D-Hawaii, said.

Correll pointed out that neither China nor Russia has conducted a nuclear explosive test, but then said, “I’m not reading anything into it or reading anything out of it.”

Daryl Kimball, the executive director of the Washington-based Arms Control Association, quickly criticized the president’s announcement and said Trump was “misinformed and out of touch.”

Kimball, in social media posts, said the U.S. has no reason to resume nuclear explosive testing and it would take at least 36 months to resume testing at the former test site in Nevada, where the last detonations occurred underground.