President-elect Trump has spent parts of the holiday season vowing to take over the Panama Canal, calling for the U.S. to buy Greenland from Denmark and suggesting Canada could become the 51st state.

Treaties ratified by the Senate in 1978 established permanent neutrality, but some Republicans regret that decision.

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.