President Donald Trump said Thursday he's nominating his national security adviser Mike Waltz to serve as United Nations ambassador in a major shake-up of his national security team. The president said Secretary of State Marco Rubio will serve simultaneously as acting national security adviser while maintaining his position at the State Department. MORE: https://www.wthr.com/article/news/nation-world/trump-national-security-advisor-mike-waltz-leaving-administration/507-24721337-13db-4d9d-b720-a51b88d49534