WASHINGTON — After the United States delivered an ultimatum to Russia last week that it was preparing to abandon a landmark weapons treaty, drawing a combative response from President Vladimir V. Putin, the specter of a rekindled nuclear arms race was widely seen as a rewind of the Cold War.

But that encompasses only one slice of the problem — and perhaps the easiest part to manage.

The United States and Russia no longer have a monopoly on the missiles that Ronald Reagan and Mikhail S. Gorbachev agreed in 1987 to ban with the Intermediate-Range Nuclear Forces, or I.N.F., agreement. Today, China relies on similar missiles for 95 percent of its ground-based fleet, and Iran, India, Saudi Arabia, North Korea and Taiwan are among the 10 states with similar, fast-growing arsenals.

In a reflection of the Trump administration’s view of how to navigate a new, more threatening global order, Washington seems uninterested in trying to renegotiate the treaty to embrace all the countries that now possess the weapons, which can carry conventional or atomic warheads. Instead, it is moving to abandon the accord and, with an eye on China, deploy in Asia the sorts of arms it pulled from Europe in the perilous days before the fall of the Berlin Wall.

The administration blames Russian violations — denied by Moscow — for the demise of what until now has been considered one of the most successful of the Cold War arms control agreements. But the bigger issue is that President Trump wants to throw off what he sees as constraints from countering other rising powers, principally China.