Trump stuns with call to resume nuclear tests — why now, and what it could mean

President Donald Trump’s announcement that the U.S. would revive nuclear weapons testing — which the U.S. has not done since 1992 — left experts, lawmakers and military personnel scratching their heads Thursday.

The president announced, just before his high-stakes meeting with Chinese President Xi Jinping, he is instructing the Pentagon to start testing nuclear weapons on an "equal basis" as Russia and China, and that the process for testing these weapons would begin immediately.  

"They seem to all be nuclear testing," Trump later told reporters on Air Force One. "We don’t do testing — we halted it years ago. But with others doing testing, it’s appropriate that we do also."

It’s unclear exactly what Trump meant, since no country has conducted a known nuclear test since North Korea in 2017. The last known tests for China and Russia date back to the 1990s, when Russia was still the Soviet Union.

TRUMP LIFTS VEIL ON US SUBMARINES IN WARNING SHOT TO KREMLIN IN 'CLEVER' REPOSITIONING MOVE

The White House did not provide comment to Fox News Digital. And the Pentagon did not respond to a request for comment. 

However, those dissecting the president's comments say Trump may have been referring to ramping up testing of nuclear-powered weapons systems or conducting covert, low-yield nuclear weapons testing.

Andrea Stricker, the deputy director of the Foundation for Defense of Democracies’ nonproliferation and biodefense program, described the announcement as a "power move" from Trump ahead of Xi’s meeting, and said that one option the president may be considering is authorizing low-yield nuclear explosive testing, but would go above the zero-yield threshold outlined in the Comprehensive Test Ban Treaty from 1996 that bans all nuclear explosions.

Although ratification from the U.S. and several other countries is necessary in order for the treaty to take effect, the pact established no nuclear testing as a worldwide norm and the U.S., Russia and China have since maintained a moratorium on full-scale nuclear testing.

TRUMP CONFIRMS 2 NUCLEAR SUBMARINES ARE 'IN THE REGION' TO COUNTER RUSSIA

However, Stricker said that the U.S. has detailed in multiple reports that it suspects that Russia and China may have conducted low-yield type tests for years, despite the moratorium laid out in the Comprehensive Test Ban Treaty. For example, now-retired Lt. Gen. Robert Ashley Jr. said in 2019, while serving as the director of the Defense Intelligence Agency, that the U.S. believes Russia isn’t adhering to the nuclear testing moratorium "in a manner consistent with the zero-yield standard."

As a result, Stricker said that Trump’s comments indicate he will match what near-peer adversaries’ actions.

"The president's statement implies reciprocity: he will increase testing as they do, which puts the onus on Moscow and Beijing to rein in their efforts," Stricker said in a Thursday email to Fox News Digital. "Trump may also be seeking to engage both countries in arms control talks with the remaining nuclear arms treaty between the United States and Russia, New START, set to expire in February 2026 and China refusing such talks."

PUTIN PRAISES TRUMP’S ‘SINCERE’ PEACE EFFORTS, SIGNALS POSSIBLE US-RUSSIA NUCLEAR DEAL

Meanwhile, Navy Vice Adm. Richard Correll, who Trump nominated to lead U.S. Strategic Command, told lawmakers Thursday during his confirmation hearing that although he didn’t have insight into Trump’s thinking, the president may have been discussing testing nuclear-powered weapon delivery systems, like ballistic and cruise missiles.

Correll said that since neither China nor Russia has conducted a nuclear test to his knowledge, he’s "not reading anything into it or out of it" when lawmakers on the Senate Armed Services Committee asked about the president’s statement. However, Correll said he’d be prepared to carry out the president’s directive if he is confirmed.

U.S. Strategic Command is a combatant command that oversees nuclear deterrence for the U.S. military.

TRUMP ORDERS US NUCLEAR WEAPONS TESTING TO BEGIN 'IMMEDIATELY' AFTER RUSSIA TESTS NEW MISSILES

Matthew Kroenig, the vice president and senior director of the Atlantic Council’s Scowcroft Center for Strategy and Security, told Fox News Digital that Russia’s recent missile test also "gives credence" to the possibility that Trump meant testing these nuclear-powered weapon delivery systems.

Russia announced Sunday that it had successfully tested its new, nuclear-powered Burevestnik cruise missile, which NATO has dubbed "Skyfall." The announcement came after the Trump administration imposed stringent sanctions on Russia’s two largest oil companies.

Kroenig, who previously worked on nuclear and defense policy at the Pentagon and helped craft the 2018 U.S. Nuclear Posture Review, also said Trump’s statement could signal an end to the Comprehensive Test Ban Treaty. 

Chairman of the Senate Foreign Relations Committee Sen. Jim Risch, R-Idaho, told reporters Thursday that it's paramount the president respond accordingly to actors, like Russian President Vladimir Putin, who have nuclear weapons.

"When you have a madman that has nuclear weapons like Putin does and he starts rattling his saber, it's important for the president to respond," Risch said. "And he responded in a way that is reasonable."

Democrats had a different take. The top Democrat on the Senate Armed Services Committee Sen. Jack Reed, D-R.I., said that Trump "has it wrong" on nuclear weapons policy, and said resuming nuclear weapons testing could upend decades of nonproliferation efforts.

"Breaking the explosive testing moratorium that the United States, Russia, and China have maintained since the 1990s would be strategically reckless, inevitably prompting Moscow and Beijing to resume their own testing programs," Reed said in a statement Thursday. "Further, American explosive testing would provide justification for Pakistan, India, and North Korea to expand their own testing regimes, destabilizing an already fragile global nonproliferation architecture at precisely the moment we can least afford it.

"The United States would gain very little from such testing, and we would sacrifice decades of hard-won progress in preventing nuclear proliferation," Reed said. 

Meanwhile, Vice President JD Vance told reporters Thursday that while the president would continue to work on nuclear proliferation, that testing would be done to ensure weapons are functioning at optimal capability.

"It's an important part of American national security to make sure that this nuclear arsenal we have actually functions properly," Vance said. "And that's part of a testing regime. To be clear, we know that it does work properly, but you got to keep on top of it over time. And the president just wants to make sure that we do that with his nation."

Fox News’ Chad Pergram and The Associated Press contributed to this report.