Debate continues over whether to invite Ukraine to join NATO Podcast appearance. John R. Deni As leaders of the North Atlantic Treaty Organization, or NATO, meet at the annual summit in Vilnius, Lithuania, the conversation continues over whether to invite Ukraine to join the alliance and if so, when. Here & Now‘s Celeste Headlee speaks with John Deni, research professor at the U.S. Army War College and a nonresident senior fellow at the Atlantic Council.