Russian leaders have their own security concerns, since they are geographically close to several nations, including North Korea, China, India and Pakistan, that have growing intermediate-range missile forces, and because the United States has a formidable advantage in sea-based and air-launched missiles.

But unilaterally abrogating one of the most consequential arms agreements in history would be dangerous and cause new tensions with European allies who are already skeptical of Mr. Trump’s commitments to the continent’s security and don’t want the United States to abandon the treaty.

By announcing plans to withdraw, as the president did with earlier agreements on climate change, Asian trade and Iran’s nuclear program, he is again undercutting American global leadership and putting the United States in position to be blamed for the I.N.F. Treaty’s collapse, rather than Russia, the actual culprit.

It would be even more harmful to let New Start, with its mandated caps on nuclear warhead deployments and valuable requirements for verification and data exchanges, unravel. Unlike the I.N.F. Treaty, New Start restrains core Russian strategic forces that could directly target the United States, not just its allies.

The Russian violation of the I.N.F. Treaty centers on an SSC-8 land-based cruise missile. American officials say it can carry nuclear and conventional warheads, is fired from a mobile launcher and has been tested at a distance of between 300 and 3,000 miles, the range prohibited by the treaty. The missiles, located in western and central Russia, are intended to intimidate Europe, especially former Soviet states aligned with the West.

But Russia so far probably has no more than 50 of them , a relatively small number. While threatening to Europe, the missile doesn’t change the balance of power with the United States. And Washington has other weapons, not prohibited by the treaty, to counter it.

Which encourages speculation that the administration may be more interested in abandoning the I.N.F. Treaty so that it can deploy medium-range missiles to Asia. China is a growing threat that relies on similar missiles for 95 percent of its ground-based fleet. It also is not part of the treaty and is not restricted in its missile development. That same goes for Iran, India, Saudi Arabia, North Korea and the other six countries with fast-growing missile arsenals.