U.S. Seeks to Build World Pressure on Russia Over Space Nuclear Weapon

American officials are trying to increase international pressure on Russia not to deploy an antisatellite nuclear weapon in space, and have obtained information that undermines Moscow’s explanation that the device it is developing is for peaceful scientific purposes, a senior State Department official said on Friday.

Concern over the Russian development of a new generation of space nuclear weapons has been growing in Washington, especially since Moscow’s veto last month of a U.N. measure aimed at keeping space free of such weapons. Some Republicans believe that the Biden administration is not doing enough to deter Russian work on the device, and others are concerned about China’s apparent decision not to pressure Moscow to stop.

On Friday, Mallory Stewart, the assistant secretary of state for arms control, said that while the United States had been aware of Russia’s pursuit of such a device for years, “only recently have we been able to make a more precise assessment of their progress.”

Ms. Stewart, speaking at the nonpartisan Center for Strategic and International Studies in Washington, said the orbit the Russian satellite would occupy is in a high-radiation region not used by other satellites, information that undercuts Russia’s defense that it is not developing a weapon.

She condemned Russia’s veto of a U.N. Security Council resolution pushed by the United States and Japan aimed at reaffirming the ban against nuclear weapons being deployed in orbit. She argued that every country should be pushing Russia not to deploy a nuclear-armed satellite.

“Everything that we’re doing in the diplomatic arena is working to prevent the Russians from going forward with this program,” she said. “The international response should be outrage