WARSAW, Poland — The United States’ special representative for Ukraine says he hopes that Russia will still “make peace and withdraw from eastern Ukraine” and that if it does, Washington stands ready to play a role in the transition.

Kurt Volker said Wednesday in Warsaw that the United States has suggested to Russia that a United Nations-mandated force could provide security following a Russian withdrawal of troops, and is waiting to hear Moscow’s response.

Volker said he remains hopeful that Moscow will agree because of the huge cost Russia is paying in military costs, casualties, frozen ties with the US and European Union, and the fact that as the conflict drags on it is producing a Ukraine “more nationalist, more unified, more Western-oriented, more anti-Russian, frankly, than has ever existed before.”