Secretary of State Marco Rubio says President Donald Trump’s desire to acquire Greenland and retake control of the Panama Canal is driven by legitimate national security interests stemming from growing concerns about Chinese activity and influence in the Arctic and in Latin America.

Panamanian President Jose Raul Mulino on Thursday ruled out discussing control over the Panama Canal in a meeting with U.S. Secretary of State Marco Rubio, who is set to visit the Central American country in his first official trip abroad this weekend.

US senators heard sharply different analyses about Chinese influence over the Panama Canal on Wednesday, with some experts suggesting solutions ranging from enhanced trade partnerships to military intervention to regain control of the strategic waterway.