BRUSSELS—U.S. and European Union leaders are converging toward supporting a plan under which two Balkan countries would redraw their fraught common border along ethnic lines, isolating Germany, the continent’s most influential power, in its rejection of that approach, a confidential document shows.
A recent memo by the EU’s foreign service about how to solve a decade-old standoff between Serbia and Kosovo, reviewed by The Wall Street Journal, shows the EU’s executive body has essentially adopted Washington’s argument and...