The United States will consider rotating additional U.S. troops through NATO member countries on Europe’s eastern flank, should Russia mount a full-scale invasion of Ukraine, and NATO would also bulk up its presence in those countries with forces and armaments, U.S. and European officials said.

The White House has repeatedly warned Russian President Vladimir Putin that if he is concerned about NATO’s presence near the Russian border now, that posture will only increase if he chooses to invade Ukraine. Already, eastern European members of the alliance are clamoring for more U.S. forces as a deterrent against an irredentist Kremlin that once controlled their lands in addition to Ukraine.

But despite the warnings to Putin from the White House, the Biden administration hasn’t detailed what an enhanced presence would look like on NATO’s eastern border after a full-scale Russian invasion of Ukraine. Nor have warnings about a bolstered NATO halted Russia’s buildup of forces, missiles and armored vehicles around Ukraine.