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.

Rubio said he could not predict if Trump would succeed in buying Greenland from Denmark or restoring American authority over the Panama Canal while he is in office.

China's influence on the Panama Canal is a major risk to U.S. national security, Sen. Ted Cruz told lawmakers during a Senate hearing on Capitol Hill.