CORRECTING DATE TO 20 - In this Aug. 15, 2019, photo, a boat navigates at night next to icebergs in eastern Greenland.  U.S. President Trump announced his decision to postpone a visit to Denmark by tweet on Tuesday Aug. 20, 2019, after Danish Prime Minister Mette Frederiksen dismissed the notion of selling Greenland to the U.S. as "an absurd discussion." (AP Photo/Felipe Dana)