Secretary of State Marco Rubio embarks soon on his inaugural trip as the United States’ top diplomat. His first stop, Panama could prove to be the most contentious on the itinerary.

During Monday’s inauguration, Donald Trump repeated his threat to retake the Panama Canal. The United States controlled the waterway since the early 20th century, but in 1977 President Jimmy Carter signed a landmark treaty to give Panama control of the canal.

In recent weeks, when he was President-elect Donald Trump publicly said that Panama should return the Panama Canal to the United States, and he would not rule out using military force to reclaim it. At his presidential Inauguration on Monday Trump doubled down on saying that his new administration was going to take back the canal.

The neutrality of the nearly 50-mile canal, through which nearly 15,000 ships transit each year, is enshrined in Panama’s Constitution and is enforced by the autonomous Panama Canal Authority.

The Panamanian leader added he will not allow his country’s “total superiority” of the shipping channel to be lessened.

In his first interview, President Trump's newly appointed head of the Federal Maritime Commission, Louis Sola, lays out how the administration plans to challenge Chinese influence at the key global trade gateway,