On a visit to the Armenian capital, Yerevan, a top U.S. diplomat welcomed the order demarcation deal signed last month by Armenia and Azerbaijan as a “momentous” step, despite concerns that further progress has been slow. James O’Brien, the U.S. Assistant Secretary of State for European and Eurasian Affairs, told RFE/RL’s Heghine Buniatyan that the two countries have a rare chance to build a lasting peace and open the way for new trade routes across the region.