Donald Trump told reporters at the White House before embarking on Marine One that his daughter, Ivanka, would be 'incredible' for the role of US ambassador to the UN but he would face accusations of nepotism if he selected her. 'I'm not sure there's anybody more competent in the world, but that's OK,' the US president said. 'But we are looking at numerous people.' Nikki Haley announced her resignation from the post earlier in the day.