Trump’s Test Threat Could Fuel Nuclear Tensions With China

When President Trump called for nuclear testing, shortly before talks with the Chinese leader Xi Jinping, he may have inadvertently added a new complication to one of the most difficult issues between their countries: their nuclear weapons rivalry.

Mr. Trump declared on Thursday that “because of other countries testing programs, I have instructed the Department of War to start testing our Nuclear Weapons on an equal basis.” His order may have been prompted by a claim by President Vladimir V. Putin, a few days earlier, that Russia had successfully test-flown a nuclear-powered and nuclear-capable cruise missile, even though the test did not involve a detonation.

Moves toward renewed explosive tests of nuclear warheads would further endanger the treaty that for decades has constrained all but a handful of countries from carrying them out. If the United States follows through with resuming nuclear testing, “it would effectively give, I think, China and Russia a carte blanche to resume full-yield nuclear testing, which is something that neither country has done in a number of years,” said Ankit Panda, the author of “The New Nuclear Age.”

“The nuclear nonproliferation regime is under tremendous stress at the moment. Russia, China, the United States can’t even agree on the basic principles of what really makes the nonproliferation regime tick,” said Mr. Panda, a senior fellow at the Carnegie Endowment for International Peace.

Mr. Trump and his administration may clarify his comments in the coming hours or days. Mr. Panda and other experts said Mr. Trump may have meant that he wants to test-launch nuclear-capable missiles, not detonate nuclear devices underground.

When asked later about his remarks on nuclear weapons testing, Mr. Trump suggested that they were not related to China. “It had to do with others,” he said, without naming any countries. “They seem to all be nuclear testing.”

But Mr. Trump’s combative words alone could reinforce wariness in Beijing about U.S. nuclear intentions. Nuclear weapons are one area where distrust between China and the United States has deepened, with little prospect for quick agreement.

Under Mr. Xi, China has been rapidly building up its nuclear arsenal after decades of maintaining a comparatively modest force. China has about 600 nuclear warheads, most of them designed for land-based missiles, according to a survey published earlier this year by experts at the Federation of American Scientists. That is still far fewer than the thousands of nuclear warheads that the United States and Russia have.

“Russia has nearly completed their modernization of all of their nuclear forces, and China is modernizing, and they are growing their arsenal at a breathtaking speed,” Elbridge A. Colby, the undersecretary of defense in the Trump administration, told senators during his confirmation hearing earlier this year.

China’s next development plan, released in summary this week, calls “strengthened strategic deterrence capabilities” — a term that includes nuclear forces — a military priority for the next five years. And last month, China displayed its growing collection of nuclear-capable missiles, including ones that can be launched from submarines and bomber planes, at a military parade in Beijing.

Mr. Xi used the parade to emphasize China’s maturing “nuclear triad,” that is, the ability to threaten enemies with nuclear attack from land, sea and air, said Lin Po-chou, a researcher at the Institute for National Defense and Security Research, a government-funded group in Taipei, Taiwan.

The pace of China’s nuclear expansion “will continue and won’t change just because of Trump’s announcement on increasing nuclear weapons testing,” Mr. Lin said.

Satellite evidence suggests that China may be making facilities ready to conduct nuclear tests underground, possibly to signal that it could respond in kind if other countries resume testing.

China conducted its first nuclear test in 1964 and its last in 1996, just before the Comprehensive Nuclear-Test-Ban Treaty, a global moratorium on testing, was adopted by most countries. (China, like the United States, signed but has not ratified the treaty.)

China carried out about 45 tests in total, fewer than the many hundreds conducted by the United States or Russia. As a result, China’s nuclear weapons scientists probably have had to work with less data than other superpowers to design their warheads. Since 1996, China and other atomic powers have checked and tested warheads by using “sub-critical tests” that stop short of atomic blasts.

But satellite imagery has revealed renewed construction at Lop Nur, China’s nuclear test site in Xinjiang, a far western region of the country. The activity includes new tunnels that could be used for underground nuclear tests, which may help in the design of new nuclear weapons, two experts, Renny Babiarz and Jason Wang, wrote in a recent study of the area.

If Mr. Trump actually orders new nuclear tests, it would take the United States about 18 months to prepare the likely test site in Nevada, said Mr. Panda, the expert at the Carnegie Endowment for International Peace. China and Russia, he said, could probably move a bit faster.

Amy Chang Chien and Erica L. Green contributed reporting.