On Jan. 26, the Bulletin of the Atomic Scientists, whose board of sponsors I chair, reset its Doomsday Clock to 2 minutes, 30 seconds to midnight — the closest it has been to midnight in more than 60 years. At the time, two of the factors we mentioned in making our decision were ominous developments in North Korea, and the frivolous and dangerous language the new American president had employed before his inauguration regarding nuclear weapons and nuclear war.

Many observers have wondered whether the events of the past weeks mean that we are even closer to Armageddon than the bulletin envisaged just seven months ago. We decide at designated annual intervals whether to move the hands of the clock. At this point, things aren’t looking good for the next assessment, in November. North Korea’s latest batch of intercontinental ballistic missiles appears to have the capability of reaching the United States, and The Washington Post reported that U.S. intelligence believes Pyongyang has managed to miniaturize its nuclear warheads to fit in the nose of those ICBMs.

This is still a far cry from having true nuclear weapons capability. It’s likely the North hasn’t met the technical challenge of managing the massive amounts of heat generated when a ballistic missile re-enters Earth’s atmosphere headed for its target. Still, Kim Jong Un’s military has moved far faster and further in ICBM and nuclear weapons development than many had predicted even a year ago.

In response to these developments, Donald Trump’s “fire and fury” statements are, as usual with the president, murky at best. Secretary of State Rex Tillerson quickly tried to dial back the tension by saying Trump’s extemporaneous comments were primarily rhetorical. Defense Secretary James Mattis, on the other hand, issued his own ominous statement that the North should “cease any considerations of actions that would lead to the end of its regime and destruction of its people.” Then, last Thursday and Friday, Trump doubled down, saying the U.S. was “locked and loaded” for the confrontation.

Certainly, the fact that Tillerson and the State Department appear to take a back seat in the Trump administration to military solutions cannot be lost on the leadership in North Korea. To step back from the brink, both parties need to be reminded that nuclear war is unwinnable.

Any direct military confrontation between North Korea and the U.S. would be devastating, and the likelihood that a conventional conflict would escalate into nuclear war is sufficiently high to give any rational actor pause. Millions could die in North and South Korea alone. The physical effects would be global ( a “limited” nuclear war, using 50-100 weapons, could affect climate and in turn agriculture worldwide, resulting in perhaps a billion deaths over a decade), and the political, economic and social consequences in our integrated world would be equally catastrophic.

North Korea obviously views the actions of the United States, and to some extent those of the rest of the world, as an effort to destabilize the existing regime. Washington needs to make its focus clearly the North’s nuclear ambitions, and nothing else. As recently as 2005 (albeit before Kim Jong Un’s ascension), the North publicly signed onto the goal of eventual denuclearization of the entire Korean peninsula.

Diplomatic initiatives probably require direct talks, the kind of dialogue President Reagan and Soviet leader Mikhail Gorbachev conducted. The Trump administration could show that it would take negotiations seriously by backing away from its attacks on another nuclear deal, the Iran agreement, instead of seeking to undo it. And the U.S. could finally use this opportunity to affirm a “no first use” policy, instead of implicitly threatening a pre-emptive strike. Any one of these moves could help turn back the hands of the Doomsday Clock.

Doomsday calculations also must weigh pronouncements like the statement released last week by one of Trump’s key evangelical advisors, Robert Jeffress: “God has given Trump authority to take out Kim Jong Un.” Perhaps Jeffress is hoping for Armageddon, and a subsequent second coming of Christ. At least Trump appears to be courting the religious right to solidify his political base, not because he actually shares their beliefs. Jeffress’ comment would be more worrisome if Mike Pence, a fundamentalist Christian, were president.

Last week marked the 72nd anniversary of the first use of a nuclear weapon against a civilian population, at Hiroshima and Nagasaki, Japan. Before President Truman dropped the second bomb, he warned the Japanese to expect “a rain of ruin … the like of which has never been seen on this earth,” language remarkably similar to Trump’s. But Truman knew there would be no retaliation. He could rely on what Trump cannot: a monopoly on atomic weapons.

The Bulletin of the Atomic Scientists and the Doomsday Clock were established by the very physicists who worked on those first bombs, and their successors have continued the task of warning the world of the dangers of nuclear war. However accurately the clock conveys the threat, it cannot make us safe. After Hiroshima and Nagasaki, Albert Einstein said, “Everything has changed, save the way we think.” We must pressure our political leaders to adjust their thinking, and their actions, to the horrifying realities we face from nuclear weapons.

Lawrence M. Krauss, a theoretical physicist, has been chairman of the board of sponsors of the Bulletin of the Atomic Scientists since 2007. His latest book is “The Greatest Story Ever Told … So Far.” He wrote this for the Los Angeles Times.