( CNN ) -- The United States and Japan started joint military exercises Friday , the Japanese defense ministry said , as tensions simmered on the Korean peninsula . About 10,500 U.S. service members are taking part in the drills , officials said . The `` Keen Sword '' exercise will continue until December 10 on military sites in Okinawa , mainland Japan and the waters surrounding it , according to officials . `` Keen Sword will cap the 50th anniversary of the Japan-U.S. alliance as an 'alliance of equals , ' '' said Maj. William Vause , chief of operational plans , training and exercises . `` It is the largest bilateral exercise between the United States and Japan military forces . [ The exercise ] will better enhance both of our countries ' readiness to respond to varied crisis situations . '' The drill is not directed to any nation , officials said . `` The goal of Keen Sword is to increase and improve our bilateral relationship to further enhance the Japan and U.S. alliance , '' Vause said , `` and to provide a realistic training environment that allows Japan Self Defense Force and U.S. forces to respond to a wide range of situations . '' The drill starts days after South Korea and the United States wrapped up joint military exercises on the Yellow Sea .
The ` ` Keen Sword '' exercise will continue until December 31 . About 300 U.S. service ##men are taking part in the drills .