Oct 23 (Reuters) - U.N. Secretary General Antonio Guterres, in a phone call with Saudi King Salman Bin Abdulaziz, welcomed initiatives announced by the kingdom on Saturday to reduce emissions of greenhouse gases, the Saudi Press Agency said. Saudi Crown Prince Mohammed bin Salman said the world"s top oil exporter aims to reach "net zero" emissions of greenhouse gases - mostly produced by burning fossil fuels - by 2060 - 10 years later than the United States.