Top diplomats from South Korea and Iran have held a phone call, spelling out concerns on developments in the Strait of Hormuz, South Korea confirmed an exchange between Foreign Affairs Minister Cho Hyun and his Iranian counterpart Abbas Araghchi had taken place at Tehran's request. Iran is reportedly working with Gulf states to resolve the disruption in the waterway. The need for resolution is becoming more pressing as reports point to Iran-backed Houthi rebels taking control of an island at the mouth of the Bab-el Mandeb Strait. Bab el-Mandeb is on the opposite side of Hormuz, linking Asia and Europe. Nick Harper reports from Washington DC.