Steven Andreasen, director for defense policy and arms control on the National Security Council staff from 1993 to 2001, is a national security consultant who teaches at the University of Minnesota.

Quietly and under a shadow of unease at home and abroad, the Trump administration is opening the door to U.S. resumption of underground nuclear explosive testing. If the president follows his national security team into this dark room, it could shatter the 50-year international consensus behind preventing the spread of nuclear weapons and launch a new nuclear arms race that shakes both the Nevada desert and one of the last remaining pillars of arms control.

The 1996 Comprehensive Nuclear-Test-Ban Treaty (CTBT ) prohibits “any nuclear weapon test explosion or any other nuclear explosion” in the atmosphere, in space, underwater or underground. During the negotiations, the United States, Russia, China, Britain and France also agreed on a “not all-inclusive, but illustrative” list of activities not prohibited by the CTBT, recorded by President Bill Clinton in a 1997 directive and given to the Senate. As the U.S. negotiator told the Senate in 1999, “the zero line, between what would be prohibited to all under the treaty and what would not be prohibited, would be precisely defined by the question of nuclear yield” — that is, whether the activity produced a self-sustaining nuclear reaction. “If what you did produced any yield whatsoever, it was not allowed. If it didn’t, it was allowed.”

Rep. Alexandria Ocasio-Cortez (D-N.Y.) on April 2 criticized the Trump administration over alleged security clearance impropriety. (The Washington Post)

The CTBT, unratified though it is by the United States, but with 184 signatories, created a near-universal norm against nuclear explosive testing. (Only North Korea has tested since 1998.) Beyond this benefit, the commitment by the five nuclear weapon states to conclude the treaty by 1996 was crucial to achieving the indefinite extension in 1995 of the existing nuclear Non-Proliferation Treaty. Today, the Non-Proliferation Treaty remains central to limiting the spread of nuclear weapons. Any action that weakens the test-ban treaty weakens the Non-Proliferation Treaty.

So why would the Trump administration seek to restart nuclear testing? In March, four Republican senators wrote the president asking whether he would consider “unsigning” the CTBT, calling the pact a “deeply flawed treaty that purports to ban all nuclear weapons tests.” In late May, the director of the Defense Intelligence Agency stated Russia “probably” is not adhering to its nuclear testing moratorium. The word “probably” prompted more queries and a new DIA statement: “The U.S. government, including the Intelligence Community, has assessed that Russia has conducted nuclear weapons tests that have created nuclear yield.”

Are the Russians cheating? Russia’s nuclear test site has been under close scrutiny for years. But in the absence of more public information — information that if it exists would probably be highly classified and unlikely to be made public — we have little choice but to assess the administration’s charge based on its motivations and methods.

Ahead of his second summit with North Korean dictator Kim Jong Un, President Trump reiterated that he wants full denuclearization of the socialist nation. (The Washington Post)

National security adviser John Bolton and other administration officials are fervent test-ban treaty opponents. The seemingly out-of-the-blue letter from Republican senators and the DIA director’s public remarks had the look of an orchestrated campaign — significantly with no apparent effort to engage with Moscow. More suspicious, someone in the Trump administration is leaking portions of the classified Clinton directive on activities not prohibited by the treaty, arguing the language “not all-inclusive, but illustrative” suggests uncertainty over the treaty’s ban. Anyone familiar with the directive and the test-ban treaty negotiating record would understand how completely misleading this is.

The CTBT balanced a ban on nuclear explosive testing with protecting the United States’ ability to maintain the safety and reliability of its own nuclear stockpile. The treaty had the strong support of all national security agencies, Cabinet officials, the Joint Chiefs of Staff and our nuclear weapons laboratories — a remarkable consensus — and has underpinned the success of our nuclear weapon labs and their maintenance of our nuclear stockpile for more than 20 years.

If the United States has evidence that nuclear-yield producing testing has been done by Russia, we should discuss it in the new strategic stability dialogue agreed to by President Trump and Russian President Vladi­mir Putin. We should reopen channels between our nuclear-weapons experts to discuss ways to build confidence that such tests are not happening. In the meantime, the United States has a robust nuclear deterrent. That deterrent would not be undermined by possible nuclear testing that the United States might fail to detect under the test-ban treaty.

The move to “unsign” the CTBT could lead to more destructive nuclear capabilities in the hands of potential U.S. adversaries and be perceived by non-nuclear-weapon states as the ultimate “bait and switch” two decades after the Non-Proliferation Treaty was extended indefinitely. It would fuel uncertainty bordering on chaos for the future of nuclear nonproliferation. And it would generate controversy around our own weapons laboratories, which play a vital role in our security. It would be a high price to pay for fulfilling the dreams of those who seek to destroy another treaty.

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