President Donald Trump said the U.S. would match its rivals in testing nuclear weapons after Russia in recent days announced trials of a nuclear-powered underwater drone and nuclear-capable cruise missile.

“Because of other countries’ testing programs, I have instructed the Department of War to start testing our Nuclear Weapons on an equal basis,” Trump said in a social media post shortly before meeting China’s leader in South Korea on Thursday. “That process will begin immediately.”

Trump appeared to be reacting to Russia’s accelerated testing of so-called nuclear-capable super weapons in recent weeks. On Wednesday, Russia said it tested an atomic-powered torpedo drone capable of carrying nuclear weapons days after its military hailed a trial of a long-distance cruise missile.

The White House didn’t immediately respond to a request for clarification over whether Trump was ordering tests of nuclear-powered weapons and those that can carry nuclear warheads, rather than nuclear detonations.

In remarks later on a flight back to the U.S. from South Korea, Trump provided no further clarity but said an announcement would be made about tests. “We don’t do testing. We’ve halted it years, many years ago, but with others doing testing, I think it’s appropriate that we do also,” he said.

The U.S.’s last nuclear explosive test was in 1992, though it continues to test delivery systems — including intercontinental ballistic missiles, submarines and bombers — with mock weapons. Russia is the only other nation with a nuclear arsenal on par with the U.S. Its last known nuclear detonation was in 1990.

Trump’s social media post came hours before a meeting with Chinese President Xi Jinping. Trump has previously expressed interest in brokering a nuclear treaty with China to reduce nuclear stockpiles, though the Chinese have resisted the U.S. president’s pitch to join nonproliferation talks.

Neither side appeared to have brought up nuclear weapons during the Thursday gathering, according to public statements they have made about the exchange.

In 2019, the U.S. withdrew from a landmark nuclear disarmament treaty with Russia because it said Moscow had violated the treaty with the production of missiles banned under the agreement. Trump said at the time that the treaty was problematic because it didn’t include China, a rising nuclear weapons power.

While China has a much smaller arsenal of nuclear warheads than the U.S. and Russia, it is rapidly increasing its inventory, according to U.S. government assessments. China last tested a nuclear bomb in 1996, but it continues to tests nuclear-capable missiles, including hypersonic missiles that are hard for missile defense systems to destroy.

The U.S., Russia and China have all signed an international treaty banning nuclear weapons tests. At a regular press briefing on Thursday, Guo Jiakun, a spokesman for the Chinese Foreign Ministry, said that Beijing “hopes that the U.S. will earnestly abide by its obligations under the comprehensive nuclear test ban treaty and its commitment to a moratorium on nuclear testing.”

Trump’s latest remarks on nuclear weapons come as efforts to broker ceasefire talks with Ukraine have faltered. Earlier this week, Trump said the cruise missile test championed by Vladimir Putin was “not appropriate” and that the Russian president should focus on ending the war with Ukraine.

On Monday, Trump brushed off security concerns over Russia’s tests by noting the U.S. had a nuclear submarine “right off” its shores.

“We test missiles all the time,” he added.

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