Secretary of State Marco Rubio embarks this weekend on his first foreign trip in office. He's heading to Central America to press President Donald Trump’s top priority — curbing illegal immigration — and bring the message that the U.

Secretary of State Marco Rubio said on Thursday he had "zero doubt" that China has a contingency plan to shut down the Panama Canal in the event of a conflict with the U.S. and that Washington intends to address what it sees as a national security threat.