Trump again suggests US could annex Greenland, hints at Nato's role / NATO chief to visit US, meet with Trump / Trump casts doubt on NATO solidarity, despite it aiding the U.S. after Sept. 11 / Trump casts doubt on NATO solidarity, despite it aiding the US after Sept. 11 / Nato countries are in a 'hidden cyber war' with Russia, says Liz Kendall / Trump's NATO tightrope: Reforming the alliance while wrangling Capitol Hill / Alliances like Nato out of touch with world in need of human security / Republicans to NATO leaders: Take Trump seriously, not literally / NATO summit in Washington a shameful event that escalates tensions -- senior diplomat / UN spokesman reminds NATO world can be safe only if it is free of nuclear weapons