(ANSA) - BELGRADE, APR 28 - US Energy Secretary Chris Wright spoke today and tomorrow in Dubrovnik, Croatia, on the sidelines of the Three Seas Initiative (3SI) summit, calling for a significant expansion of natural gas market infrastructure, describing it as a "affordable and clean" energy source. As President Donald Trump's envoy to the summit of 13 EU countries, he emphasised that the US is the world's largest natural gas exporter, calling for new infrastructure investments in the US, Europe, and Croatia, and citing the LNG terminal on the Croatian island of Krk (Veglia in Italian), in the northern Adriatic, as a model for a Croatian-American partnership serving the entire region. (ANSA).