At first, he joked about Canada being an additional US state. Since, he has threatened to take back control of the Panama Canal. He also reiterated a desire from his first term to own the autonomous Danish territory of Greenland, which is not for sale.

It's unclear how the issue of ownership of the Panama Canal became a talking point for President-elect Donald Trump this week, but the question has a long political history.

Trump again having designs on Greenland comes after the president-elect suggested over the weekend that the U.S. could retake control of the Panama Canal if something isn't done to ease rising shipping costs required for using the waterway linking the Atlantic and Pacific oceans.