U.S. Considers Expanded Nuclear Arsenal, a Reversal of Decades of Cuts

A senior Biden administration official warned on Friday that “absent a change” in nuclear strategy by China and Russia, the United States may be forced to expand its nuclear arsenal, after decades of cutting back through now largely abandoned arms control agreements.

The comments on Friday from Pranay Vaddi, a senior director of the National Security Council, were the most explicit public warning yet that the United States was prepared to shift from simply modernizing its arsenal to expanding it. They were also a warning to President Vladimir V. Putin of Russia about the likely U.S. reaction if the last major nuclear arms control agreement, called New START, expires in February 2026 with no replacement.

Mr. Vaddi, speaking at the annual meeting of the Arms Control Association, a group that advocates limits on nuclear weapons, confirmed what officials have been saying in private conversations and closed congressional testimony for more than a year. It is the inevitable outgrowth, they have argued, of China’s rapid nuclear expansion and Russia’s repeated threats to use tactical nuclear weapons in Ukraine.

But it would be an epochal shift, and one fraught with dangers that many Americans thought they had left behind at the end of the Cold War and the collapse of the Soviet Union.

Fifteen years ago, President Barack Obama outlined a vision of moving toward a world without nuclear weapons, and he took steps to reduce their role in American strategy and defenses. While the nation’s nuclear complexes were improved and made safer, and old weapons were swapped out for more reliable or updated versions, the United States insisted it was only “modernizing” its arsenal, not expanding it.

As vice president in the Obama administration,