The U.S. State Department on Monday warned Americans against travel to Japan, citing a surge in COVID-19 cases in the country. 

The department posted the update on its website, raising its travel advisory for Japan by one notch to the highest "Level Four: Do Not Travel."

The Level Four advisory announcement comes less than two months before the scheduled July 23 opening ceremony for the Tokyo Olympic Games. 

The U.S. operates a four-tier travel alert system - Level One: Exercise Normal Precautions, Level Two: Exercise Increased Caution, Level Three: Reconsider Travel and Level Four: Do Not Travel.
  
South Korea is currently under Level Two.