Panama has complained to the United Nations over United States President Donald Trump's "worrying" threat to seize the Panama Canal, even as it launched an audit of the Hong Kong-linked operator of two ports on the interoceanic waterway.

The Panamanian comptroller's office that oversees public entities announced “an exhaustive audit" at the Panama Ports Company.

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.