A U.S. government investigation has found that Myanmar's military waged a planned, coordinated campaign of mass killings, gang rapes and other atrocities against the Southeast Asian nation's Rohingya Muslim minority.

The State Department report, reviewed by Reuters ahead of its expected public release on Monday, could be used to justify further U.S. sanctions or other punitive measures against Myanmar authorities, said U.S. officials.

But it stopped short of describing the crackdown as genocide or crimes against humanity, an issue that other U.S. officials said was the subject of fierce internal debate that delayed the report's roll-out for nearly a month.