NATO launches Arctic Sentry effort amid pressure from President Donald Trump about security in the region, and his calls for U.S. acquisition of Greenland.

Nato chief Mark Rutte joked about Donald Trump's invasion threat, at the Western allies' first high-level meeting since the peak in the Greenland crisis.

Nato has launched a new Arctic mission — but on paper only, as Western allies try to mop up the mess left by US invasion threats against Greenland.