Some U.S. lawmakers and officials are touting a nearly half-century-old treaty between the United States and Panama to justify the Trump administration's threat to reclaim the Panama Canal - provided it can show the strategic waterway's operation is under threat.

The U.S. and Panama are apprehensive about China's presence around the Panama Canal, citing national security concerns. The issue will be a focus during U.S. top diplomat Marco Rubio's visit, where he will meet Panamanian President Jose Raul Mulino and discuss regional migration issues.

Jose Raul Mulino said he won't discuss control of the canal during the secretary of state's visit. Rubio, in contrast, said "we're going to address that topic."