WASHINGTON, Nov 1 - President Donald Trump on Thursday said he is seriously considering naming U.S. State Department spokeswoman Heather Nauert to succeed Nikki Haley as U.S. Ambassador to the United Nations, adding he would make a decision on the posting soon."She is under very serious consideration," Trump told reporters at the White House after announcing planned changes to U.S. immigration policy. "She's excellent. She's been with us for a very long time. She's been a supporter for a long time... We'll probably make a decision next week."