The United States has established diplomatic relations with Montenegro, which voted in May to break away from Serbia, according to dpa. US President George W Bush and Montenegrin President Filip Vujanovic exchanged letters formally establishing diplomatic ties, US State Department spokesman Sean McCormack said Tuesday. In a May 21 referendum, Montenegro seceded from the union with Serbia, and two weeks later the United States recognized the Balkan state as an independent country, pledging to move forward on creating diplomatic relations. "The United States looks forward to continued friendship and cooperation with the people of Montenegro," McCormack said in a statement.