NIGER'S junta has demanded that the head of the United Nations diplomatic mission there leave the country within 72 hours, accusing the U.N. of excluding Niger from its General Assembly last month. The army officers who seized power in a coup in July did not have a representative at the meeting of world leaders in New York. A U.N. spokesperson in Niamey said she had no immediate comment. In a statement dated October 10, Niger's foreign ministry accused the U.N. of using "underhanded manoeuvres" instigated by France to prevent its full participation in the U.N. General Assembly and in subsequent…