President Zelensky says that the American negotiations raised the possibility that Ukraine would give up its remaining territory in the Donbass in exchange for NATO membership. Kyiv still controls about 20% of the region, including the heavily fortified Slovansk. The Kramatorsk defense belt, which Russian forces were unable to capture despite years of fighting and massive losses.
The proposal raises serious strategic concerns. Surrendering the fortress belt and strategically important high ground would leave Ukraine in a much more vulnerable defensive position, and allow Russia to extend its UAV coverage further west by exploiting the elevated terrain. Moscow will also inherit the defensive positions that Ukraine has spent years strengthening, and may be based in much the same way as Ukrainian forces are today. Even with NATO membership, these would be huge military and geographic concessions, making such an agreement difficult.