American rapper Nicki Minaj is scheduled to deliver a speech at the United Nations on Tuesday at 1:30 p.m. ET to bring international attention to the massacre of Christians in Nigeria, US Ambassador to the UN Mike Waltz announced on Monday.The Starships singer was credited by Waltz on Monday to be “the greatest female recording artist” and a “principled individual who refuses to remain silent in the face of injustice.”Tuesday at 1:30pm ET — I'm welcoming @NICKIMINAJ to the U.S. Mission for a