(BELGRADE, Serbia) — U.S. President Donald Trump’s special envoy for Serbia and Kosovo said Saturday that an agreement to resume railway service between the two Balkan rivals is important for both nations. Richard Grenell, who is the U.S. ambassador to Germany, said establishing train links became a priority after U.S. officials brokered another deal earlier this week to restore air traffic between the countries after 21 years. Grenell visited Pristina, the capital of Kosovo, and Serbia’s capital of Belgrade this week.