The U.S. acknowledgment this week that the Pentagon is operating weapons in Earth’s orbit marks a landmark moment in space militarization aimed at deterring what U.S. officials describe as aggressive orbital activities from China and Russia, officials and analysts said.

U.S. Space Force chief Gen. Douglas Schiess said Tuesday that enlisted members of his military branch “operate on-orbit weapons that can defend the Joint Force against space-enabled attacks.” The service will make “disciplined and responsible choices” as it scales its orbital defense arsenal in the coming years, he added.

Schiess’ remarks at a conference near Washington came a day after U.S. Air Force Secretary Troy Meink said the U.S. “has on-orbit space control weapons capable of defending the Joint Force against hostile adversary action.” That was the clearest admission yet by a Pentagon official of U.S. weapons in orbit amid rising space tensions with Russia and China.