NEW YORK (Reuters) - The United States is worried about the  tragedies  in Myanmar affecting Rohingya Muslims and U.S. authorities are pressing government leader Aung San Suu Kyi and Myanmar s military leaders to stop the crackdown, U.S. Ambassador to the United Nations Nikki Haley said on Thursday.  Not only have we pressed her, we pressed the military,  Haley told reporters, referring to Suu Kyi. She said U.S. Joint Chiefs of Staff Chairman General Joseph Dunford was calling the head of Myanmar s military to say  this cannot continue.  