I do not think that it was US idea. In fact, when the first news of the breakthrough came in, US was suprised and not encouraging. I was shocked then at the speed with which US changed the tune, and suddenly wanted to have "the lead role" and get the credit for it. I personally believe that this was work of Turkish and Armenian leadership, facilitated by Moscow for a long time. Multiple meetings were held with Armenian and Azerbaijani leadership to insure that roadblocks are removed, and some issues set aside for the sake of making first steps. US has little to cheer. Border opening could create conditions for a safe energy transit route from Azerbaijan, bypassing Georgia. US has very litte leverage to press Armenia with. The powerfull diaspora is now split, and it will be interesting to see who gets the mighty funding thus far enjoyed by the Armenian diaspora in US. That may be very telling.