Senior officers from countries across Europe and beyond were due to meet Thursday at a military headquarters on the outskirts of London to flesh out plans for an international peacekeeping force for Ukraine as details of a partial ceasefire are worked out.

UK Prime Minister Keir Starmer said the “coalition of the willing” plan, led by Britain and France, is moving into an “operational phase”. But it’s unclear how many countries are willing to send troops, or whether there will be any ceasefire to protect.