When Russia conducted a series of secret military satellite launches around the time of its invasion of Ukraine in early 2022, American intelligence officials began delving into the mystery of what, exactly, the Russians were doing.

Later, spy agencies discovered Russia was working on a new kind of space-based weapon that could threaten the thousands of satellites that keep the world connected.

In recent weeks, a new warning has circulated from America’s spy agencies: Another launch may be in the works, and the question is whether Russia plans to use it to put a real nuclear weapon into space — a violation of a half-century-old treaty. The agencies are divided on the likelihood that President Vladimir V. Putin would go so far, but nonetheless the intelligence is an urgent concern to the Biden administration.

Even if Russia does place a nuclear weapon in orbit, U.S. officials are in agreement in their assessment that the weapon would not be detonated. Instead, it would lurk as a time bomb in low orbit, a reminder from Mr. Putin that if he was pressed too hard with sanctions, or military opposition to his ambitions in Ukraine or beyond, he could destroy economies without targeting humans on earth.

Despite […]