Taken along with Trump’s trolling on Canada becoming part of America and now wanting Greenland as an “absolute necessity” it could be interpreted as a threat. I doubt Denmark will appreciate being pressured to sell it as it is their largest landmass. His comments are very expansionist.
China wants to include Greenland in its Belt and Road Initiative and it wants to get its paws on Greenland's natural resources.
That is out of the question.
If the U.S. doesn't take action to remove access to Greenland (i.e., out of China's reach), China will clearly move to make sure Greenland—with its rare earth assets and strategic location—is out of our reach.
That cannot be permitted.