For the White House, these have been dramatic days for nuclear disarmament: First President Trump exited the Iran deal, demanding that Tehran sign a new agreement that forever cuts off its path to making a bomb, then the administration announced a first-ever meeting with the leader of North Korea about ridding his nation of nuclear weapons.
But for the American arsenal, the initiatives are all going in the opposite direction, with a series of little-noticed announcements to spend billions of dollars building the factories needed to rejuvenate and expand America’s nuclear capacity.
The contrast has been striking. On Thursday evening, hours after Mr. Trump announced that his meeting with Kim Jong-un, the North Korean leader, would take place on June 12 in Singapore, the Pentagon and the Energy Department announced plans to begin building critical components for next-generation nuclear weapons at the Savannah River Site in South Carolina.
The idea is to repurpose a half-built, problem-ridden complex that was originally intended to turn old nuclear weapons into reactor fuel to light American cities. Now the facility will be used to revitalize America’s aging nuclear weapons, and to create the capacity to make many hundreds more.
The Pentagon, in its main nuclear strategy report released in February, cited North Korea’s ability to “illicitly produce nuclear warheads” as a major justification for the new effort.
Also last week, a strategic forces subcommittee in the House approved Trump administration plans to build a new kind of low-yield nuclear weapon, launched from submarines, to match Russian nuclear advances.
The chairman of the subcommittee, Mike D. Rogers, Republican of Alabama, said the decision was a reaction to the new arms race with Moscow. Mr. Trump said in March that he intended to meet with President Vladimir V. Putin to discuss the arms race, which he said was “getting out of control.” (No such meeting has yet been scheduled.)
“This committee knows what Russia’s up to with its nuclear weapons,” Mr. Rogers said. “It’s both sobering and horrifying.”
While it is possible that the American buildup is part of a negotiating strategy, offering Mr. Trump something he can trade away before it gets started, the White House has made clear, in both statements and strategy, that it envisions the reduction of nuclear weapons as a one-way street.
It is hardly the first time the United States has seen no inconsistency in expanding its own nuclear capabilities while trying to persuade lesser powers to give up theirs.
In fact, the imbalance is built into the Nuclear Nonproliferation Treaty, which went into effect in 1970. It prohibits all states that did not already have the bomb from building nuclear weapons. (Israel, Pakistan and India never joined, and North Korea dropped out.)
But it also requires the acknowledged nuclear powers — the United States, Russia, China, Britain and France — to work toward “the cessation of the nuclear arms race and to nuclear disarmament,” and ultimately to complete their own disarmament.
For the two decades after the fall of the Berlin Wall, both the United States and Russia could argue that they were making progress on that promise. The number of nuclear weapons deployed by the two countries fell, and fell again, under a series of arms control agreements, and as of earlier this year, both are now limited to 1,550 deployed weapons. Thousands more are in storage.
President Barack Obama argued that the United States could not urge other countries to give up nuclear programs while expanding its own. But many of his own aides later said they wished he had done far more to reduce America’s arsenal, arguing that it could safely drop below the number the Russians deployed.
Now Mr. Trump is heading in the other direction. The United States has dramatically stepped up the effort to overhaul the existing arsenal and prepare for the day when it might once again be enlarged. Unless the New Start Treaty is renewed for five years, any limits on the American and Russian arsenals will expire in February 2021, just days after Mr. Trump would enter his second term.
In the meantime, the American government is doing all it can to make clear it is preparing for an era of nuclear buildup.
At the center of the Savannah River announcement is the American production of something the nuclear industry calls “pits.” That is a term for a small atom bomb that, when detonated inside a warhead, acts as an extraordinarily hot match to ignite a much larger mass of thermonuclear fuel. The resulting blast can easily be 1,000 times as powerful as the atomic bomb that destroyed Hiroshima.
One of the most closely held secrets of the nuclear age is how to make pits very small yet highly reliable. Most are about the size of a grapefruit. The small size makes thermonuclear warheads compact and lightweight enough to fit atop long-range missiles — it is one of the technologies that North Korea has been seeking, and may have already figured out.
The announcement on Thursday sought to make lemonade out of two large federal lemons.
The pits have been made, until now, at the Los Alamos weapons laboratory in New Mexico, where America’s first nuclear weapons were built. But the lab has suffered a humiliating string of operating and safety failures, which in 2015 led the Obama administration to announce plans to end the current management contract there. Among the breakdowns was the management’s failure to come up with a credible plan for producing up to 80 pits a year.
At the same time, cost estimates for the Savannah River project to turn tons of excess weapons-grade plutonium into fuel for commercial power reactors had soared to $17 billion.
Now that project is scrapped, and the two-pronged plan announced on Thursday will also take the production pressure off Los Alamos — a move that seeks to maintain its profile as a scientific research center rather than as a munitions factory.
Los Alamos is to make 30 pits per year, and the South Carolina plant 50. That setup, the Energy and Defense Departments said, will improve “the resiliency, flexibility and redundancy of our nuclear security enterprise by not relying on a single production site.” But it also signals a return to production of new weapons, even as Mr. Trump is withdrawing from the 2015 deal with Iran in part because of “sunset provisions” that he says will eventually allow Tehran to do the same.
The federal rationale for making up to 80 pits a year is hidden in layers of secrecy but turns on stated fears that the plutonium fuel at the heart of American weapons will deteriorate with age, eventually rendering them useless.
Whether that fear is justified is a matter of debate. In 2006, a federal nuclear panel found that the plutonium pits aged far better than expected, with most able to work reliably for a century or more.
That judgment led critics to contend that the federal government was seeking a new generation of nuclear pits for reasons not of national security but of saber-rattling.
“No new pits are needed for any warhead,” Greg Mello, the executive director of the Los Alamos Study Group, a private organization in Albuquerque that monitors the nation’s nuclear complex and opposes expansion, said recently. “There are thousands of pits stockpiled for possible reuse.”
The Pentagon’s Nuclear Posture Review, published in February, called for the new capability to produce plutonium pits. It also called on Congress to approve the new low-yield nuclear weapons.
Last week, the full House Armed Services Committee endorsed the Nuclear Posture Review, but with Democrats overwhelmingly voting against it.
“We have to have a credible deterrence, but I think the Nuclear Posture Review goes way beyond credible nuclear deterrence,” said Representative Adam Smith of Washington, the top Democrat on the committee, warning that “we could stumble into a nuclear war.”