The idea for a buffer zone to protect Ukraine, part of a tentative plan to guarantee its security, would have to be agreed upon in any peace deal.

If a peace deal between Russia and Ukraine ever comes together, the United States could take the lead role in monitoring a large buffer zone inside Ukraine envisioned as a way to protect the country from Russia, according to four people familiar with a plan that military officials from Ukraine’s allies, including the United States, have been discussing.

The buffer zone would be a large demilitarized area — the borders of which have not yet been decided — inside what is now Ukraine, dividing Russian and Ukrainian territory within the country. In part because of its technological capabilities, the United States would take the lead in watching the buffer zone, using drones and satellites along with other intelligence capabilities, but it would coordinate with other countries that would also monitor.